java中多线程中Runnable接口和Thread类介绍

时间:2022-10-23 17:31:44

java中的线程时通过调用操作系统底层的线程来实现线程的功能的。

先看如下代码,并写出输出结果。

// 请问输出结果是什么?
    public static void main(String[] args) {
        new Thread(new Runnable() {

            public void run() {
                System.out.println("Runnable running..");
            }
            
        }) {

            public void run() {
                System.out.println("Thread running..");
            };
        }.start();
    }

结果是:"Thread running.."

    首先,如果你能说出答案,说明你的基础还是很不错的。如果说不出来也没关系,那么我们可以一起来学习一下java中Thread的源码实现了。我们都知道java(jdk8以前,<据说java8中有新的可以实现线程的方法>)中实现线程最常用的两种实现线程的方式时继承thread和实现Runnable接口。那么就让我们一起来分析一下这两种方式的源码吧。

我们先看一下Runnable接口的源码:

 1 @FunctionalInterface
 2 public interface Runnable {
 3     /**
 4      * When an object implementing interface <code>Runnable</code> is used
 5      * to create a thread, starting the thread causes the object's
 6      * <code>run</code> method to be called in that separately executing
 7      * thread.
 8      * <p>
 9      * The general contract of the method <code>run</code> is that it may
10      * take any action whatsoever.
11      *
12      * @see     java.lang.Thread#run()
13      */
14     public abstract void run();
15 }

以下是Thread类源码:

java中多线程中Runnable接口和Thread类介绍java中多线程中Runnable接口和Thread类介绍
   1 /*
   2  * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
   4  *
   5  *
   6  *
   7  *
   8  *
   9  *
  10  *
  11  *
  12  *
  13  *
  14  *
  15  *
  16  *
  17  *
  18  *
  19  *
  20  *
  21  *
  22  *
  23  *
  24  */
  25 
  26 package java.lang;
  27 
  28 import java.lang.ref.Reference;
  29 import java.lang.ref.ReferenceQueue;
  30 import java.lang.ref.WeakReference;
  31 import java.security.AccessController;
  32 import java.security.AccessControlContext;
  33 import java.security.PrivilegedAction;
  34 import java.util.Map;
  35 import java.util.HashMap;
  36 import java.util.concurrent.ConcurrentHashMap;
  37 import java.util.concurrent.ConcurrentMap;
  38 import java.util.concurrent.locks.LockSupport;
  39 import sun.nio.ch.Interruptible;
  40 import sun.reflect.CallerSensitive;
  41 import sun.reflect.Reflection;
  42 import sun.security.util.SecurityConstants;
  43 
  44 
  45 /**
  46  * A <i>thread</i> is a thread of execution in a program. The Java
  47  * Virtual Machine allows an application to have multiple threads of
  48  * execution running concurrently.
  49  * <p>
  50  * Every thread has a priority. Threads with higher priority are
  51  * executed in preference to threads with lower priority. Each thread
  52  * may or may not also be marked as a daemon. When code running in
  53  * some thread creates a new <code>Thread</code> object, the new
  54  * thread has its priority initially set equal to the priority of the
  55  * creating thread, and is a daemon thread if and only if the
  56  * creating thread is a daemon.
  57  * <p>
  58  * When a Java Virtual Machine starts up, there is usually a single
  59  * non-daemon thread (which typically calls the method named
  60  * <code>main</code> of some designated class). The Java Virtual
  61  * Machine continues to execute threads until either of the following
  62  * occurs:
  63  * <ul>
  64  * <li>The <code>exit</code> method of class <code>Runtime</code> has been
  65  *     called and the security manager has permitted the exit operation
  66  *     to take place.
  67  * <li>All threads that are not daemon threads have died, either by
  68  *     returning from the call to the <code>run</code> method or by
  69  *     throwing an exception that propagates beyond the <code>run</code>
  70  *     method.
  71  * </ul>
  72  * <p>
  73  * There are two ways to create a new thread of execution. One is to
  74  * declare a class to be a subclass of <code>Thread</code>. This
  75  * subclass should override the <code>run</code> method of class
  76  * <code>Thread</code>. An instance of the subclass can then be
  77  * allocated and started. For example, a thread that computes primes
  78  * larger than a stated value could be written as follows:
  79  * <hr><blockquote><pre>
  80  *     class PrimeThread extends Thread {
  81  *         long minPrime;
  82  *         PrimeThread(long minPrime) {
  83  *             this.minPrime = minPrime;
  84  *         }
  85  *
  86  *         public void run() {
  87  *             // compute primes larger than minPrime
  88  *             &nbsp;.&nbsp;.&nbsp;.
  89  *         }
  90  *     }
  91  * </pre></blockquote><hr>
  92  * <p>
  93  * The following code would then create a thread and start it running:
  94  * <blockquote><pre>
  95  *     PrimeThread p = new PrimeThread(143);
  96  *     p.start();
  97  * </pre></blockquote>
  98  * <p>
  99  * The other way to create a thread is to declare a class that
 100  * implements the <code>Runnable</code> interface. That class then
 101  * implements the <code>run</code> method. An instance of the class can
 102  * then be allocated, passed as an argument when creating
 103  * <code>Thread</code>, and started. The same example in this other
 104  * style looks like the following:
 105  * <hr><blockquote><pre>
 106  *     class PrimeRun implements Runnable {
 107  *         long minPrime;
 108  *         PrimeRun(long minPrime) {
 109  *             this.minPrime = minPrime;
 110  *         }
 111  *
 112  *         public void run() {
 113  *             // compute primes larger than minPrime
 114  *             &nbsp;.&nbsp;.&nbsp;.
 115  *         }
 116  *     }
 117  * </pre></blockquote><hr>
 118  * <p>
 119  * The following code would then create a thread and start it running:
 120  * <blockquote><pre>
 121  *     PrimeRun p = new PrimeRun(143);
 122  *     new Thread(p).start();
 123  * </pre></blockquote>
 124  * <p>
 125  * Every thread has a name for identification purposes. More than
 126  * one thread may have the same name. If a name is not specified when
 127  * a thread is created, a new name is generated for it.
 128  * <p>
 129  * Unless otherwise noted, passing a {@code null} argument to a constructor
 130  * or method in this class will cause a {@link NullPointerException} to be
 131  * thrown.
 132  *
 133  * @author  unascribed
 134  * @see     Runnable
 135  * @see     Runtime#exit(int)
 136  * @see     #run()
 137  * @see     #stop()
 138  * @since   JDK1.0
 139  */
 140 public
 141 class Thread implements Runnable {
 142     /* Make sure registerNatives is the first thing <clinit> does. */
 143     private static native void registerNatives();
 144     static {
 145         registerNatives();
 146     }
 147 
 148     private volatile char  name[];
 149     private int            priority;
 150     private Thread         threadQ;
 151     private long           eetop;
 152 
 153     /* Whether or not to single_step this thread. */
 154     private boolean     single_step;
 155 
 156     /* Whether or not the thread is a daemon thread. */
 157     private boolean     daemon = false;
 158 
 159     /* JVM state */
 160     private boolean     stillborn = false;
 161 
 162     /* What will be run. */
 163     private Runnable target;
 164 
 165     /* The group of this thread */
 166     private ThreadGroup group;
 167 
 168     /* The context ClassLoader for this thread */
 169     private ClassLoader contextClassLoader;
 170 
 171     /* The inherited AccessControlContext of this thread */
 172     private AccessControlContext inheritedAccessControlContext;
 173 
 174     /* For autonumbering anonymous threads. */
 175     private static int threadInitNumber;
 176     private static synchronized int nextThreadNum() {
 177         return threadInitNumber++;
 178     }
 179 
 180     /* ThreadLocal values pertaining to this thread. This map is maintained
 181      * by the ThreadLocal class. */
 182     ThreadLocal.ThreadLocalMap threadLocals = null;
 183 
 184     /*
 185      * InheritableThreadLocal values pertaining to this thread. This map is
 186      * maintained by the InheritableThreadLocal class.
 187      */
 188     ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
 189 
 190     /*
 191      * The requested stack size for this thread, or 0 if the creator did
 192      * not specify a stack size.  It is up to the VM to do whatever it
 193      * likes with this number; some VMs will ignore it.
 194      */
 195     private long stackSize;
 196 
 197     /*
 198      * JVM-private state that persists after native thread termination.
 199      */
 200     private long nativeParkEventPointer;
 201 
 202     /*
 203      * Thread ID
 204      */
 205     private long tid;
 206 
 207     /* For generating thread ID */
 208     private static long threadSeqNumber;
 209 
 210     /* Java thread status for tools,
 211      * initialized to indicate thread 'not yet started'
 212      */
 213 
 214     private volatile int threadStatus = 0;
 215 
 216 
 217     private static synchronized long nextThreadID() {
 218         return ++threadSeqNumber;
 219     }
 220 
 221     /**
 222      * The argument supplied to the current call to
 223      * java.util.concurrent.locks.LockSupport.park.
 224      * Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
 225      * Accessed using java.util.concurrent.locks.LockSupport.getBlocker
 226      */
 227     volatile Object parkBlocker;
 228 
 229     /* The object in which this thread is blocked in an interruptible I/O
 230      * operation, if any.  The blocker's interrupt method should be invoked
 231      * after setting this thread's interrupt status.
 232      */
 233     private volatile Interruptible blocker;
 234     private final Object blockerLock = new Object();
 235 
 236     /* Set the blocker field; invoked via sun.misc.SharedSecrets from java.nio code
 237      */
 238     void blockedOn(Interruptible b) {
 239         synchronized (blockerLock) {
 240             blocker = b;
 241         }
 242     }
 243 
 244     /**
 245      * The minimum priority that a thread can have.
 246      */
 247     public final static int MIN_PRIORITY = 1;
 248 
 249    /**
 250      * The default priority that is assigned to a thread.
 251      */
 252     public final static int NORM_PRIORITY = 5;
 253 
 254     /**
 255      * The maximum priority that a thread can have.
 256      */
 257     public final static int MAX_PRIORITY = 10;
 258 
 259     /**
 260      * Returns a reference to the currently executing thread object.
 261      *
 262      * @return  the currently executing thread.
 263      */
 264     public static native Thread currentThread();
 265 
 266     /**
 267      * A hint to the scheduler that the current thread is willing to yield
 268      * its current use of a processor. The scheduler is free to ignore this
 269      * hint.
 270      *
 271      * <p> Yield is a heuristic attempt to improve relative progression
 272      * between threads that would otherwise over-utilise a CPU. Its use
 273      * should be combined with detailed profiling and benchmarking to
 274      * ensure that it actually has the desired effect.
 275      *
 276      * <p> It is rarely appropriate to use this method. It may be useful
 277      * for debugging or testing purposes, where it may help to reproduce
 278      * bugs due to race conditions. It may also be useful when designing
 279      * concurrency control constructs such as the ones in the
 280      * {@link java.util.concurrent.locks} package.
 281      */
 282     public static native void yield();
 283 
 284     /**
 285      * Causes the currently executing thread to sleep (temporarily cease
 286      * execution) for the specified number of milliseconds, subject to
 287      * the precision and accuracy of system timers and schedulers. The thread
 288      * does not lose ownership of any monitors.
 289      *
 290      * @param  millis
 291      *         the length of time to sleep in milliseconds
 292      *
 293      * @throws  IllegalArgumentException
 294      *          if the value of {@code millis} is negative
 295      *
 296      * @throws  InterruptedException
 297      *          if any thread has interrupted the current thread. The
 298      *          <i>interrupted status</i> of the current thread is
 299      *          cleared when this exception is thrown.
 300      */
 301     public static native void sleep(long millis) throws InterruptedException;
 302 
 303     /**
 304      * Causes the currently executing thread to sleep (temporarily cease
 305      * execution) for the specified number of milliseconds plus the specified
 306      * number of nanoseconds, subject to the precision and accuracy of system
 307      * timers and schedulers. The thread does not lose ownership of any
 308      * monitors.
 309      *
 310      * @param  millis
 311      *         the length of time to sleep in milliseconds
 312      *
 313      * @param  nanos
 314      *         {@code 0-999999} additional nanoseconds to sleep
 315      *
 316      * @throws  IllegalArgumentException
 317      *          if the value of {@code millis} is negative, or the value of
 318      *          {@code nanos} is not in the range {@code 0-999999}
 319      *
 320      * @throws  InterruptedException
 321      *          if any thread has interrupted the current thread. The
 322      *          <i>interrupted status</i> of the current thread is
 323      *          cleared when this exception is thrown.
 324      */
 325     public static void sleep(long millis, int nanos)
 326     throws InterruptedException {
 327         if (millis < 0) {
 328             throw new IllegalArgumentException("timeout value is negative");
 329         }
 330 
 331         if (nanos < 0 || nanos > 999999) {
 332             throw new IllegalArgumentException(
 333                                 "nanosecond timeout value out of range");
 334         }
 335 
 336         if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
 337             millis++;
 338         }
 339 
 340         sleep(millis);
 341     }
 342 
 343     /**
 344      * Initializes a Thread with the current AccessControlContext.
 345      * @see #init(ThreadGroup,Runnable,String,long,AccessControlContext)
 346      */
 347     private void init(ThreadGroup g, Runnable target, String name,
 348                       long stackSize) {
 349         init(g, target, name, stackSize, null);
 350     }
 351 
 352     /**
 353      * Initializes a Thread.
 354      *
 355      * @param g the Thread group
 356      * @param target the object whose run() method gets called
 357      * @param name the name of the new Thread
 358      * @param stackSize the desired stack size for the new thread, or
 359      *        zero to indicate that this parameter is to be ignored.
 360      * @param acc the AccessControlContext to inherit, or
 361      *            AccessController.getContext() if null
 362      */
 363     private void init(ThreadGroup g, Runnable target, String name,
 364                       long stackSize, AccessControlContext acc) {
 365         if (name == null) {
 366             throw new NullPointerException("name cannot be null");
 367         }
 368 
 369         this.name = name.toCharArray();
 370 
 371         Thread parent = currentThread();
 372         SecurityManager security = System.getSecurityManager();
 373         if (g == null) {
 374             /* Determine if it's an applet or not */
 375 
 376             /* If there is a security manager, ask the security manager
 377                what to do. */
 378             if (security != null) {
 379                 g = security.getThreadGroup();
 380             }
 381 
 382             /* If the security doesn't have a strong opinion of the matter
 383                use the parent thread group. */
 384             if (g == null) {
 385                 g = parent.getThreadGroup();
 386             }
 387         }
 388 
 389         /* checkAccess regardless of whether or not threadgroup is
 390            explicitly passed in. */
 391         g.checkAccess();
 392 
 393         /*
 394          * Do we have the required permissions?
 395          */
 396         if (security != null) {
 397             if (isCCLOverridden(getClass())) {
 398                 security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
 399             }
 400         }
 401 
 402         g.addUnstarted();
 403 
 404         this.group = g;
 405         this.daemon = parent.isDaemon();
 406         this.priority = parent.getPriority();
 407         if (security == null || isCCLOverridden(parent.getClass()))
 408             this.contextClassLoader = parent.getContextClassLoader();
 409         else
 410             this.contextClassLoader = parent.contextClassLoader;
 411         this.inheritedAccessControlContext =
 412                 acc != null ? acc : AccessController.getContext();
 413         this.target = target;
 414         setPriority(priority);
 415         if (parent.inheritableThreadLocals != null)
 416             this.inheritableThreadLocals =
 417                 ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
 418         /* Stash the specified stack size in case the VM cares */
 419         this.stackSize = stackSize;
 420 
 421         /* Set thread ID */
 422         tid = nextThreadID();
 423     }
 424 
 425     /**
 426      * Throws CloneNotSupportedException as a Thread can not be meaningfully
 427      * cloned. Construct a new Thread instead.
 428      *
 429      * @throws  CloneNotSupportedException
 430      *          always
 431      */
 432     @Override
 433     protected Object clone() throws CloneNotSupportedException {
 434         throw new CloneNotSupportedException();
 435     }
 436 
 437     /**
 438      * Allocates a new {@code Thread} object. This constructor has the same
 439      * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
 440      * {@code (null, null, gname)}, where {@code gname} is a newly generated
 441      * name. Automatically generated names are of the form
 442      * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
 443      */
 444     public Thread() {
 445         init(null, null, "Thread-" + nextThreadNum(), 0);
 446     }
 447 
 448     /**
 449      * Allocates a new {@code Thread} object. This constructor has the same
 450      * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
 451      * {@code (null, target, gname)}, where {@code gname} is a newly generated
 452      * name. Automatically generated names are of the form
 453      * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
 454      *
 455      * @param  target
 456      *         the object whose {@code run} method is invoked when this thread
 457      *         is started. If {@code null}, this classes {@code run} method does
 458      *         nothing.
 459      */
 460     public Thread(Runnable target) {
 461         init(null, target, "Thread-" + nextThreadNum(), 0);
 462     }
 463 
 464     /**
 465      * Creates a new Thread that inherits the given AccessControlContext.
 466      * This is not a public constructor.
 467      */
 468     Thread(Runnable target, AccessControlContext acc) {
 469         init(null, target, "Thread-" + nextThreadNum(), 0, acc);
 470     }
 471 
 472     /**
 473      * Allocates a new {@code Thread} object. This constructor has the same
 474      * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
 475      * {@code (group, target, gname)} ,where {@code gname} is a newly generated
 476      * name. Automatically generated names are of the form
 477      * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
 478      *
 479      * @param  group
 480      *         the thread group. If {@code null} and there is a security
 481      *         manager, the group is determined by {@linkplain
 482      *         SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
 483      *         If there is not a security manager or {@code
 484      *         SecurityManager.getThreadGroup()} returns {@code null}, the group
 485      *         is set to the current thread's thread group.
 486      *
 487      * @param  target
 488      *         the object whose {@code run} method is invoked when this thread
 489      *         is started. If {@code null}, this thread's run method is invoked.
 490      *
 491      * @throws  SecurityException
 492      *          if the current thread cannot create a thread in the specified
 493      *          thread group
 494      */
 495     public Thread(ThreadGroup group, Runnable target) {
 496         init(group, target, "Thread-" + nextThreadNum(), 0);
 497     }
 498 
 499     /**
 500      * Allocates a new {@code Thread} object. This constructor has the same
 501      * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
 502      * {@code (null, null, name)}.
 503      *
 504      * @param   name
 505      *          the name of the new thread
 506      */
 507     public Thread(String name) {
 508         init(null, null, name, 0);
 509     }
 510 
 511     /**
 512      * Allocates a new {@code Thread} object. This constructor has the same
 513      * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
 514      * {@code (group, null, name)}.
 515      *
 516      * @param  group
 517      *         the thread group. If {@code null} and there is a security
 518      *         manager, the group is determined by {@linkplain
 519      *         SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
 520      *         If there is not a security manager or {@code
 521      *         SecurityManager.getThreadGroup()} returns {@code null}, the group
 522      *         is set to the current thread's thread group.
 523      *
 524      * @param  name
 525      *         the name of the new thread
 526      *
 527      * @throws  SecurityException
 528      *          if the current thread cannot create a thread in the specified
 529      *          thread group
 530      */
 531     public Thread(ThreadGroup group, String name) {
 532         init(group, null, name, 0);
 533     }
 534 
 535     /**
 536      * Allocates a new {@code Thread} object. This constructor has the same
 537      * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
 538      * {@code (null, target, name)}.
 539      *
 540      * @param  target
 541      *         the object whose {@code run} method is invoked when this thread
 542      *         is started. If {@code null}, this thread's run method is invoked.
 543      *
 544      * @param  name
 545      *         the name of the new thread
 546      */
 547     public Thread(Runnable target, String name) {
 548         init(null, target, name, 0);
 549     }
 550 
 551     /**
 552      * Allocates a new {@code Thread} object so that it has {@code target}
 553      * as its run object, has the specified {@code name} as its name,
 554      * and belongs to the thread group referred to by {@code group}.
 555      *
 556      * <p>If there is a security manager, its
 557      * {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
 558      * method is invoked with the ThreadGroup as its argument.
 559      *
 560      * <p>In addition, its {@code checkPermission} method is invoked with
 561      * the {@code RuntimePermission("enableContextClassLoaderOverride")}
 562      * permission when invoked directly or indirectly by the constructor
 563      * of a subclass which overrides the {@code getContextClassLoader}
 564      * or {@code setContextClassLoader} methods.
 565      *
 566      * <p>The priority of the newly created thread is set equal to the
 567      * priority of the thread creating it, that is, the currently running
 568      * thread. The method {@linkplain #setPriority setPriority} may be
 569      * used to change the priority to a new value.
 570      *
 571      * <p>The newly created thread is initially marked as being a daemon
 572      * thread if and only if the thread creating it is currently marked
 573      * as a daemon thread. The method {@linkplain #setDaemon setDaemon}
 574      * may be used to change whether or not a thread is a daemon.
 575      *
 576      * @param  group
 577      *         the thread group. If {@code null} and there is a security
 578      *         manager, the group is determined by {@linkplain
 579      *         SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
 580      *         If there is not a security manager or {@code
 581      *         SecurityManager.getThreadGroup()} returns {@code null}, the group
 582      *         is set to the current thread's thread group.
 583      *
 584      * @param  target
 585      *         the object whose {@code run} method is invoked when this thread
 586      *         is started. If {@code null}, this thread's run method is invoked.
 587      *
 588      * @param  name
 589      *         the name of the new thread
 590      *
 591      * @throws  SecurityException
 592      *          if the current thread cannot create a thread in the specified
 593      *          thread group or cannot override the context class loader methods.
 594      */
 595     public Thread(ThreadGroup group, Runnable target, String name) {
 596         init(group, target, name, 0);
 597     }
 598 
 599     /**
 600      * Allocates a new {@code Thread} object so that it has {@code target}
 601      * as its run object, has the specified {@code name} as its name,
 602      * and belongs to the thread group referred to by {@code group}, and has
 603      * the specified <i>stack size</i>.
 604      *
 605      * <p>This constructor is identical to {@link
 606      * #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
 607      * that it allows the thread stack size to be specified.  The stack size
 608      * is the approximate number of bytes of address space that the virtual
 609      * machine is to allocate for this thread's stack.  <b>The effect of the
 610      * {@code stackSize} parameter, if any, is highly platform dependent.</b>
 611      *
 612      * <p>On some platforms, specifying a higher value for the
 613      * {@code stackSize} parameter may allow a thread to achieve greater
 614      * recursion depth before throwing a {@link *Error}.
 615      * Similarly, specifying a lower value may allow a greater number of
 616      * threads to exist concurrently without throwing an {@link
 617      * OutOfMemoryError} (or other internal error).  The details of
 618      * the relationship between the value of the <tt>stackSize</tt> parameter
 619      * and the maximum recursion depth and concurrency level are
 620      * platform-dependent.  <b>On some platforms, the value of the
 621      * {@code stackSize} parameter may have no effect whatsoever.</b>
 622      *
 623      * <p>The virtual machine is free to treat the {@code stackSize}
 624      * parameter as a suggestion.  If the specified value is unreasonably low
 625      * for the platform, the virtual machine may instead use some
 626      * platform-specific minimum value; if the specified value is unreasonably
 627      * high, the virtual machine may instead use some platform-specific
 628      * maximum.  Likewise, the virtual machine is free to round the specified
 629      * value up or down as it sees fit (or to ignore it completely).
 630      *
 631      * <p>Specifying a value of zero for the {@code stackSize} parameter will
 632      * cause this constructor to behave exactly like the
 633      * {@code Thread(ThreadGroup, Runnable, String)} constructor.
 634      *
 635      * <p><i>Due to the platform-dependent nature of the behavior of this
 636      * constructor, extreme care should be exercised in its use.
 637      * The thread stack size necessary to perform a given computation will
 638      * likely vary from one JRE implementation to another.  In light of this
 639      * variation, careful tuning of the stack size parameter may be required,
 640      * and the tuning may need to be repeated for each JRE implementation on
 641      * which an application is to run.</i>
 642      *
 643      * <p>Implementation note: Java platform implementers are encouraged to
 644      * document their implementation's behavior with respect to the
 645      * {@code stackSize} parameter.
 646      *
 647      *
 648      * @param  group
 649      *         the thread group. If {@code null} and there is a security
 650      *         manager, the group is determined by {@linkplain
 651      *         SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
 652      *         If there is not a security manager or {@code
 653      *         SecurityManager.getThreadGroup()} returns {@code null}, the group
 654      *         is set to the current thread's thread group.
 655      *
 656      * @param  target
 657      *         the object whose {@code run} method is invoked when this thread
 658      *         is started. If {@code null}, this thread's run method is invoked.
 659      *
 660      * @param  name
 661      *         the name of the new thread
 662      *
 663      * @param  stackSize
 664      *         the desired stack size for the new thread, or zero to indicate
 665      *         that this parameter is to be ignored.
 666      *
 667      * @throws  SecurityException
 668      *          if the current thread cannot create a thread in the specified
 669      *          thread group
 670      *
 671      * @since 1.4
 672      */
 673     public Thread(ThreadGroup group, Runnable target, String name,
 674                   long stackSize) {
 675         init(group, target, name, stackSize);
 676     }
 677 
 678     /**
 679      * Causes this thread to begin execution; the Java Virtual Machine
 680      * calls the <code>run</code> method of this thread.
 681      * <p>
 682      * The result is that two threads are running concurrently: the
 683      * current thread (which returns from the call to the
 684      * <code>start</code> method) and the other thread (which executes its
 685      * <code>run</code> method).
 686      * <p>
 687      * It is never legal to start a thread more than once.
 688      * In particular, a thread may not be restarted once it has completed
 689      * execution.
 690      *
 691      * @exception  IllegalThreadStateException  if the thread was already
 692      *               started.
 693      * @see        #run()
 694      * @see        #stop()
 695      */
 696     public synchronized void start() {
 697         /**
 698          * This method is not invoked for the main method thread or "system"
 699          * group threads created/set up by the VM. Any new functionality added
 700          * to this method in the future may have to also be added to the VM.
 701          *
 702          * A zero status value corresponds to state "NEW".
 703          */
 704         if (threadStatus != 0)
 705             throw new IllegalThreadStateException();
 706 
 707         /* Notify the group that this thread is about to be started
 708          * so that it can be added to the group's list of threads
 709          * and the group's unstarted count can be decremented. */
 710         group.add(this);
 711 
 712         boolean started = false;
 713         try {
 714             start0();
 715             started = true;
 716         } finally {
 717             try {
 718                 if (!started) {
 719                     group.threadStartFailed(this);
 720                 }
 721             } catch (Throwable ignore) {
 722                 /* do nothing. If start0 threw a Throwable then
 723                   it will be passed up the call stack */
 724             }
 725         }
 726     }
 727 
 728     private native void start0();
 729 
 730     /**
 731      * If this thread was constructed using a separate
 732      * <code>Runnable</code> run object, then that
 733      * <code>Runnable</code> object's <code>run</code> method is called;
 734      * otherwise, this method does nothing and returns.
 735      * <p>
 736      * Subclasses of <code>Thread</code> should override this method.
 737      *
 738      * @see     #start()
 739      * @see     #stop()
 740      * @see     #Thread(ThreadGroup, Runnable, String)
 741      */
 742     @Override
 743     public void run() {
 744         if (target != null) {
 745             target.run();
 746         }
 747     }
 748 
 749     /**
 750      * This method is called by the system to give a Thread
 751      * a chance to clean up before it actually exits.
 752      */
 753     private void exit() {
 754         if (group != null) {
 755             group.threadTerminated(this);
 756             group = null;
 757         }
 758         /* Aggressively null out all reference fields: see bug 4006245 */
 759         target = null;
 760         /* Speed the release of some of these resources */
 761         threadLocals = null;
 762         inheritableThreadLocals = null;
 763         inheritedAccessControlContext = null;
 764         blocker = null;
 765         uncaughtExceptionHandler = null;
 766     }
 767 
 768     /**
 769      * Forces the thread to stop executing.
 770      * <p>
 771      * If there is a security manager installed, its <code>checkAccess</code>
 772      * method is called with <code>this</code>
 773      * as its argument. This may result in a
 774      * <code>SecurityException</code> being raised (in the current thread).
 775      * <p>
 776      * If this thread is different from the current thread (that is, the current
 777      * thread is trying to stop a thread other than itself), the
 778      * security manager's <code>checkPermission</code> method (with a
 779      * <code>RuntimePermission("stopThread")</code> argument) is called in
 780      * addition.
 781      * Again, this may result in throwing a
 782      * <code>SecurityException</code> (in the current thread).
 783      * <p>
 784      * The thread represented by this thread is forced to stop whatever
 785      * it is doing abnormally and to throw a newly created
 786      * <code>ThreadDeath</code> object as an exception.
 787      * <p>
 788      * It is permitted to stop a thread that has not yet been started.
 789      * If the thread is eventually started, it immediately terminates.
 790      * <p>
 791      * An application should not normally try to catch
 792      * <code>ThreadDeath</code> unless it must do some extraordinary
 793      * cleanup operation (note that the throwing of
 794      * <code>ThreadDeath</code> causes <code>finally</code> clauses of
 795      * <code>try</code> statements to be executed before the thread
 796      * officially dies).  If a <code>catch</code> clause catches a
 797      * <code>ThreadDeath</code> object, it is important to rethrow the
 798      * object so that the thread actually dies.
 799      * <p>
 800      * The top-level error handler that reacts to otherwise uncaught
 801      * exceptions does not print out a message or otherwise notify the
 802      * application if the uncaught exception is an instance of
 803      * <code>ThreadDeath</code>.
 804      *
 805      * @exception  SecurityException  if the current thread cannot
 806      *               modify this thread.
 807      * @see        #interrupt()
 808      * @see        #checkAccess()
 809      * @see        #run()
 810      * @see        #start()
 811      * @see        ThreadDeath
 812      * @see        ThreadGroup#uncaughtException(Thread,Throwable)
 813      * @see        SecurityManager#checkAccess(Thread)
 814      * @see        SecurityManager#checkPermission
 815      * @deprecated This method is inherently unsafe.  Stopping a thread with
 816      *       Thread.stop causes it to unlock all of the monitors that it
 817      *       has locked (as a natural consequence of the unchecked
 818      *       <code>ThreadDeath</code> exception propagating up the stack).  If
 819      *       any of the objects previously protected by these monitors were in
 820      *       an inconsistent state, the damaged objects become visible to
 821      *       other threads, potentially resulting in arbitrary behavior.  Many
 822      *       uses of <code>stop</code> should be replaced by code that simply
 823      *       modifies some variable to indicate that the target thread should
 824      *       stop running.  The target thread should check this variable
 825      *       regularly, and return from its run method in an orderly fashion
 826      *       if the variable indicates that it is to stop running.  If the
 827      *       target thread waits for long periods (on a condition variable,
 828      *       for example), the <code>interrupt</code> method should be used to
 829      *       interrupt the wait.
 830      *       For more information, see
 831      *       <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
 832      *       are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
 833      */
 834     @Deprecated
 835     public final void stop() {
 836         SecurityManager security = System.getSecurityManager();
 837         if (security != null) {
 838             checkAccess();
 839             if (this != Thread.currentThread()) {
 840                 security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
 841             }
 842         }
 843         // A zero status value corresponds to "NEW", it can't change to
 844         // not-NEW because we hold the lock.
 845         if (threadStatus != 0) {
 846             resume(); // Wake up thread if it was suspended; no-op otherwise
 847         }
 848 
 849         // The VM can handle all thread states
 850         stop0(new ThreadDeath());
 851     }
 852 
 853     /**
 854      * Throws {@code UnsupportedOperationException}.
 855      *
 856      * @param obj ignored
 857      *
 858      * @deprecated This method was originally designed to force a thread to stop
 859      *        and throw a given {@code Throwable} as an exception. It was
 860      *        inherently unsafe (see {@link #stop()} for details), and furthermore
 861      *        could be used to generate exceptions that the target thread was
 862      *        not prepared to handle.
 863      *        For more information, see
 864      *        <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
 865      *        are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
 866      */
 867     @Deprecated
 868     public final synchronized void stop(Throwable obj) {
 869         throw new UnsupportedOperationException();
 870     }
 871 
 872     /**
 873      * Interrupts this thread.
 874      *
 875      * <p> Unless the current thread is interrupting itself, which is
 876      * always permitted, the {@link #checkAccess() checkAccess} method
 877      * of this thread is invoked, which may cause a {@link
 878      * SecurityException} to be thrown.
 879      *
 880      * <p> If this thread is blocked in an invocation of the {@link
 881      * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
 882      * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
 883      * class, or of the {@link #join()}, {@link #join(long)}, {@link
 884      * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
 885      * methods of this class, then its interrupt status will be cleared and it
 886      * will receive an {@link InterruptedException}.
 887      *
 888      * <p> If this thread is blocked in an I/O operation upon an {@link
 889      * java.nio.channels.InterruptibleChannel InterruptibleChannel}
 890      * then the channel will be closed, the thread's interrupt
 891      * status will be set, and the thread will receive a {@link
 892      * java.nio.channels.ClosedByInterruptException}.
 893      *
 894      * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
 895      * then the thread's interrupt status will be set and it will return
 896      * immediately from the selection operation, possibly with a non-zero
 897      * value, just as if the selector's {@link
 898      * java.nio.channels.Selector#wakeup wakeup} method were invoked.
 899      *
 900      * <p> If none of the previous conditions hold then this thread's interrupt
 901      * status will be set. </p>
 902      *
 903      * <p> Interrupting a thread that is not alive need not have any effect.
 904      *
 905      * @throws  SecurityException
 906      *          if the current thread cannot modify this thread
 907      *
 908      * @revised 6.0
 909      * @spec JSR-51
 910      */
 911     public void interrupt() {
 912         if (this != Thread.currentThread())
 913             checkAccess();
 914 
 915         synchronized (blockerLock) {
 916             Interruptible b = blocker;
 917             if (b != null) {
 918                 interrupt0();           // Just to set the interrupt flag
 919                 b.interrupt(this);
 920                 return;
 921             }
 922         }
 923         interrupt0();
 924     }
 925 
 926     /**
 927      * Tests whether the current thread has been interrupted.  The
 928      * <i>interrupted status</i> of the thread is cleared by this method.  In
 929      * other words, if this method were to be called twice in succession, the
 930      * second call would return false (unless the current thread were
 931      * interrupted again, after the first call had cleared its interrupted
 932      * status and before the second call had examined it).
 933      *
 934      * <p>A thread interruption ignored because a thread was not alive
 935      * at the time of the interrupt will be reflected by this method
 936      * returning false.
 937      *
 938      * @return  <code>true</code> if the current thread has been interrupted;
 939      *          <code>false</code> otherwise.
 940      * @see #isInterrupted()
 941      * @revised 6.0
 942      */
 943     public static boolean interrupted() {
 944         return currentThread().isInterrupted(true);
 945     }
 946 
 947     /**
 948      * Tests whether this thread has been interrupted.  The <i>interrupted
 949      * status</i> of the thread is unaffected by this method.
 950      *
 951      * <p>A thread interruption ignored because a thread was not alive
 952      * at the time of the interrupt will be reflected by this method
 953      * returning false.
 954      *
 955      * @return  <code>true</code> if this thread has been interrupted;
 956      *          <code>false</code> otherwise.
 957      * @see     #interrupted()
 958      * @revised 6.0
 959      */
 960     public boolean isInterrupted() {
 961         return isInterrupted(false);
 962     }
 963 
 964     /**
 965      * Tests if some Thread has been interrupted.  The interrupted state
 966      * is reset or not based on the value of ClearInterrupted that is
 967      * passed.
 968      */
 969     private native boolean isInterrupted(boolean ClearInterrupted);
 970 
 971     /**
 972      * Throws {@link NoSuchMethodError}.
 973      *
 974      * @deprecated This method was originally designed to destroy this
 975      *     thread without any cleanup. Any monitors it held would have
 976      *     remained locked. However, the method was never implemented.
 977      *     If if were to be implemented, it would be deadlock-prone in
 978      *     much the manner of {@link #suspend}. If the target thread held
 979      *     a lock protecting a critical system resource when it was
 980      *     destroyed, no thread could ever access this resource again.
 981      *     If another thread ever attempted to lock this resource, deadlock
 982      *     would result. Such deadlocks typically manifest themselves as
 983      *     "frozen" processes. For more information, see
 984      *     <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">
 985      *     Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
 986      * @throws NoSuchMethodError always
 987      */
 988     @Deprecated
 989     public void destroy() {
 990         throw new NoSuchMethodError();
 991     }
 992 
 993     /**
 994      * Tests if this thread is alive. A thread is alive if it has
 995      * been started and has not yet died.
 996      *
 997      * @return  <code>true</code> if this thread is alive;
 998      *          <code>false</code> otherwise.
 999      */
1000     public final native boolean isAlive();
1001 
1002     /**
1003      * Suspends this thread.
1004      * <p>
1005      * First, the <code>checkAccess</code> method of this thread is called
1006      * with no arguments. This may result in throwing a
1007      * <code>SecurityException </code>(in the current thread).
1008      * <p>
1009      * If the thread is alive, it is suspended and makes no further
1010      * progress unless and until it is resumed.
1011      *
1012      * @exception  SecurityException  if the current thread cannot modify
1013      *               this thread.
1014      * @see #checkAccess
1015      * @deprecated   This method has been deprecated, as it is
1016      *   inherently deadlock-prone.  If the target thread holds a lock on the
1017      *   monitor protecting a critical system resource when it is suspended, no
1018      *   thread can access this resource until the target thread is resumed. If
1019      *   the thread that would resume the target thread attempts to lock this
1020      *   monitor prior to calling <code>resume</code>, deadlock results.  Such
1021      *   deadlocks typically manifest themselves as "frozen" processes.
1022      *   For more information, see
1023      *   <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
1024      *   are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1025      */
1026     @Deprecated
1027     public final void suspend() {
1028         checkAccess();
1029         suspend0();
1030     }
1031 
1032     /**
1033      * Resumes a suspended thread.
1034      * <p>
1035      * First, the <code>checkAccess</code> method of this thread is called
1036      * with no arguments. This may result in throwing a
1037      * <code>SecurityException</code> (in the current thread).
1038      * <p>
1039      * If the thread is alive but suspended, it is resumed and is
1040      * permitted to make progress in its execution.
1041      *
1042      * @exception  SecurityException  if the current thread cannot modify this
1043      *               thread.
1044      * @see        #checkAccess
1045      * @see        #suspend()
1046      * @deprecated This method exists solely for use with {@link #suspend},
1047      *     which has been deprecated because it is deadlock-prone.
1048      *     For more information, see
1049      *     <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
1050      *     are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
1051      */
1052     @Deprecated
1053     public final void resume() {
1054         checkAccess();
1055         resume0();
1056     }
1057 
1058     /**
1059      * Changes the priority of this thread.
1060      * <p>
1061      * First the <code>checkAccess</code> method of this thread is called
1062      * with no arguments. This may result in throwing a
1063      * <code>SecurityException</code>.
1064      * <p>
1065      * Otherwise, the priority of this thread is set to the smaller of
1066      * the specified <code>newPriority</code> and the maximum permitted
1067      * priority of the thread's thread group.
1068      *
1069      * @param newPriority priority to set this thread to
1070      * @exception  IllegalArgumentException  If the priority is not in the
1071      *               range <code>MIN_PRIORITY</code> to
1072      *               <code>MAX_PRIORITY</code>.
1073      * @exception  SecurityException  if the current thread cannot modify
1074      *               this thread.
1075      * @see        #getPriority
1076      * @see        #checkAccess()
1077      * @see        #getThreadGroup()
1078      * @see        #MAX_PRIORITY
1079      * @see        #MIN_PRIORITY
1080      * @see        ThreadGroup#getMaxPriority()
1081      */
1082     public final void setPriority(int newPriority) {
1083         ThreadGroup g;
1084         checkAccess();
1085         if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
1086             throw new IllegalArgumentException();
1087         }
1088         if((g = getThreadGroup()) != null) {
1089             if (newPriority > g.getMaxPriority()) {
1090                 newPriority = g.getMaxPriority();
1091             }
1092             setPriority0(priority = newPriority);
1093         }
1094     }
1095 
1096     /**
1097      * Returns this thread's priority.
1098      *
1099      * @return  this thread's priority.
1100      * @see     #setPriority
1101      */
1102     public final int getPriority() {
1103         return priority;
1104     }
1105 
1106     /**
1107      * Changes the name of this thread to be equal to the argument
1108      * <code>name</code>.
1109      * <p>
1110      * First the <code>checkAccess</code> method of this thread is called
1111      * with no arguments. This may result in throwing a
1112      * <code>SecurityException</code>.
1113      *
1114      * @param      name   the new name for this thread.
1115      * @exception  SecurityException  if the current thread cannot modify this
1116      *               thread.
1117      * @see        #getName
1118      * @see        #checkAccess()
1119      */
1120     public final synchronized void setName(String name) {
1121         checkAccess();
1122         this.name = name.toCharArray();
1123         if (threadStatus != 0) {
1124             setNativeName(name);
1125         }
1126     }
1127 
1128     /**
1129      * Returns this thread's name.
1130      *
1131      * @return  this thread's name.
1132      * @see     #setName(String)
1133      */
1134     public final String getName() {
1135         return new String(name, true);
1136     }
1137 
1138     /**
1139      * Returns the thread group to which this thread belongs.
1140      * This method returns null if this thread has died
1141      * (been stopped).
1142      *
1143      * @return  this thread's thread group.
1144      */
1145     public final ThreadGroup getThreadGroup() {
1146         return group;
1147     }
1148 
1149     /**
1150      * Returns an estimate of the number of active threads in the current
1151      * thread's {@linkplain java.lang.ThreadGroup thread group} and its
1152      * subgroups. Recursively iterates over all subgroups in the current
1153      * thread's thread group.
1154      *
1155      * <p> The value returned is only an estimate because the number of
1156      * threads may change dynamically while this method traverses internal
1157      * data structures, and might be affected by the presence of certain
1158      * system threads. This method is intended primarily for debugging
1159      * and monitoring purposes.
1160      *
1161      * @return  an estimate of the number of active threads in the current
1162      *          thread's thread group and in any other thread group that
1163      *          has the current thread's thread group as an ancestor
1164      */
1165     public static int activeCount() {
1166         return currentThread().getThreadGroup().activeCount();
1167     }
1168 
1169     /**
1170      * Copies into the specified array every active thread in the current
1171      * thread's thread group and its subgroups. This method simply
1172      * invokes the {@link java.lang.ThreadGroup#enumerate(Thread[])}
1173      * method of the current thread's thread group.
1174      *
1175      * <p> An application might use the {@linkplain #activeCount activeCount}
1176      * method to get an estimate of how big the array should be, however
1177      * <i>if the array is too short to hold all the threads, the extra threads
1178      * are silently ignored.</i>  If it is critical to obtain every active
1179      * thread in the current thread's thread group and its subgroups, the
1180      * invoker should verify that the returned int value is strictly less
1181      * than the length of {@code tarray}.
1182      *
1183      * <p> Due to the inherent race condition in this method, it is recommended
1184      * that the method only be used for debugging and monitoring purposes.
1185      *
1186      * @param  tarray
1187      *         an array into which to put the list of threads
1188      *
1189      * @return  the number of threads put into the array
1190      *
1191      * @throws  SecurityException
1192      *          if {@link java.lang.ThreadGroup#checkAccess} determines that
1193      *          the current thread cannot access its thread group
1194      */
1195     public static int enumerate(Thread tarray[]) {
1196         return currentThread().getThreadGroup().enumerate(tarray);
1197     }
1198 
1199     /**
1200      * Counts the number of stack frames in this thread. The thread must
1201      * be suspended.
1202      *
1203      * @return     the number of stack frames in this thread.
1204      * @exception  IllegalThreadStateException  if this thread is not
1205      *             suspended.
1206      * @deprecated The definition of this call depends on {@link #suspend},
1207      *             which is deprecated.  Further, the results of this call
1208      *             were never well-defined.
1209      */
1210     @Deprecated
1211     public native int countStackFrames();
1212 
1213     /**
1214      * Waits at most {@code millis} milliseconds for this thread to
1215      * die. A timeout of {@code 0} means to wait forever.
1216      *
1217      * <p> This implementation uses a loop of {@code this.wait} calls
1218      * conditioned on {@code this.isAlive}. As a thread terminates the
1219      * {@code this.notifyAll} method is invoked. It is recommended that
1220      * applications not use {@code wait}, {@code notify}, or
1221      * {@code notifyAll} on {@code Thread} instances.
1222      *
1223      * @param  millis
1224      *         the time to wait in milliseconds
1225      *
1226      * @throws  IllegalArgumentException
1227      *          if the value of {@code millis} is negative
1228      *
1229      * @throws  InterruptedException
1230      *          if any thread has interrupted the current thread. The
1231      *          <i>interrupted status</i> of the current thread is
1232      *          cleared when this exception is thrown.
1233      */
1234     public final synchronized void join(long millis)
1235     throws InterruptedException {
1236         long base = System.currentTimeMillis();
1237         long now = 0;
1238 
1239         if (millis < 0) {
1240             throw new IllegalArgumentException("timeout value is negative");
1241         }
1242 
1243         if (millis == 0) {
1244             while (isAlive()) {
1245                 wait(0);
1246             }
1247         } else {
1248             while (isAlive()) {
1249                 long delay = millis - now;
1250                 if (delay <= 0) {
1251                     break;
1252                 }
1253                 wait(delay);
1254                 now = System.currentTimeMillis() - base;
1255             }
1256         }
1257     }
1258 
1259     /**
1260      * Waits at most {@code millis} milliseconds plus
1261      * {@code nanos} nanoseconds for this thread to die.
1262      *
1263      * <p> This implementation uses a loop of {@code this.wait} calls
1264      * conditioned on {@code this.isAlive}. As a thread terminates the
1265      * {@code this.notifyAll} method is invoked. It is recommended that
1266      * applications not use {@code wait}, {@code notify}, or
1267      * {@code notifyAll} on {@code Thread} instances.
1268      *
1269      * @param  millis
1270      *         the time to wait in milliseconds
1271      *
1272      * @param  nanos
1273      *         {@code 0-999999} additional nanoseconds to wait
1274      *
1275      * @throws  IllegalArgumentException
1276      *          if the value of {@code millis} is negative, or the value
1277      *          of {@code nanos} is not in the range {@code 0-999999}
1278      *
1279      * @throws  InterruptedException
1280      *          if any thread has interrupted the current thread. The
1281      *          <i>interrupted status</i> of the current thread is
1282      *          cleared when this exception is thrown.
1283      */
1284     public final synchronized void join(long millis, int nanos)
1285     throws InterruptedException {
1286 
1287         if (millis < 0) {
1288             throw new IllegalArgumentException("timeout value is negative");
1289         }
1290 
1291         if (nanos < 0 || nanos > 999999) {
1292             throw new IllegalArgumentException(
1293                                 "nanosecond timeout value out of range");
1294         }
1295 
1296         if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
1297             millis++;
1298         }
1299 
1300         join(millis);
1301     }
1302 
1303     /**
1304      * Waits for this thread to die.
1305      *
1306      * <p> An invocation of this method behaves in exactly the same
1307      * way as the invocation
1308      *
1309      * <blockquote>
1310      * {@linkplain #join(long) join}{@code (0)}
1311      * </blockquote>
1312      *
1313      * @throws  InterruptedException
1314      *          if any thread has interrupted the current thread. The
1315      *          <i>interrupted status</i> of the current thread is
1316      *          cleared when this exception is thrown.
1317      */
1318     public final void join() throws InterruptedException {
1319         join(0);
1320     }
1321 
1322     /**
1323      * Prints a stack trace of the current thread to the standard error stream.
1324      * This method is used only for debugging.
1325      *
1326      * @see     Throwable#printStackTrace()
1327      */
1328     public static void dumpStack() {
1329         new Exception("Stack trace").printStackTrace();
1330     }
1331 
1332     /**
1333      * Marks this thread as either a {@linkplain #isDaemon daemon} thread
1334      * or a user thread. The Java Virtual Machine exits when the only
1335      * threads running are all daemon threads.
1336      *
1337      * <p> This method must be invoked before the thread is started.
1338      *
1339      * @param  on
1340      *         if {@code true}, marks this thread as a daemon thread
1341      *
1342      * @throws  IllegalThreadStateException
1343      *          if this thread is {@linkplain #isAlive alive}
1344      *
1345      * @throws  SecurityException
1346      *          if {@link #checkAccess} determines that the current
1347      *          thread cannot modify this thread
1348      */
1349     public final void setDaemon(boolean on) {
1350         checkAccess();
1351         if (isAlive()) {
1352             throw new IllegalThreadStateException();
1353         }
1354         daemon = on;
1355     }
1356 
1357     /**
1358      * Tests if this thread is a daemon thread.
1359      *
1360      * @return  <code>true</code> if this thread is a daemon thread;
1361      *          <code>false</code> otherwise.
1362      * @see     #setDaemon(boolean)
1363      */
1364     public final boolean isDaemon() {
1365         return daemon;
1366     }
1367 
1368     /**
1369      * Determines if the currently running thread has permission to
1370      * modify this thread.
1371      * <p>
1372      * If there is a security manager, its <code>checkAccess</code> method
1373      * is called with this thread as its argument. This may result in
1374      * throwing a <code>SecurityException</code>.
1375      *
1376      * @exception  SecurityException  if the current thread is not allowed to
1377      *               access this thread.
1378      * @see        SecurityManager#checkAccess(Thread)
1379      */
1380     public final void checkAccess() {
1381         SecurityManager security = System.getSecurityManager();
1382         if (security != null) {
1383             security.checkAccess(this);
1384         }
1385     }
1386 
1387     /**
1388      * Returns a string representation of this thread, including the
1389      * thread's name, priority, and thread group.
1390      *
1391      * @return  a string representation of this thread.
1392      */
1393     public String toString() {
1394         ThreadGroup group = getThreadGroup();
1395         if (group != null) {
1396             return "Thread[" + getName() + "," + getPriority() + "," +
1397                            group.getName() + "]";
1398         } else {
1399             return "Thread[" + getName() + "," + getPriority() + "," +
1400                             "" + "]";
1401         }
1402     }
1403 
1404     /**
1405      * Returns the context ClassLoader for this Thread. The context
1406      * ClassLoader is provided by the creator of the thread for use
1407      * by code running in this thread when loading classes and resources.
1408      * If not {@linkplain #setContextClassLoader set}, the default is the
1409      * ClassLoader context of the parent Thread. The context ClassLoader of the
1410      * primordial thread is typically set to the class loader used to load the
1411      * application.
1412      *
1413      * <p>If a security manager is present, and the invoker's class loader is not
1414      * {@code null} and is not the same as or an ancestor of the context class
1415      * loader, then this method invokes the security manager's {@link
1416      * SecurityManager#checkPermission(java.security.Permission) checkPermission}
1417      * method with a {@link RuntimePermission RuntimePermission}{@code
1418      * ("getClassLoader")} permission to verify that retrieval of the context
1419      * class loader is permitted.
1420      *
1421      * @return  the context ClassLoader for this Thread, or {@code null}
1422      *          indicating the system class loader (or, failing that, the
1423      *          bootstrap class loader)
1424      *
1425      * @throws  SecurityException
1426      *          if the current thread cannot get the context ClassLoader
1427      *
1428      * @since 1.2
1429      */
1430     @CallerSensitive
1431     public ClassLoader getContextClassLoader() {
1432         if (contextClassLoader == null)
1433             return null;
1434         SecurityManager sm = System.getSecurityManager();
1435         if (sm != null) {
1436             ClassLoader.checkClassLoaderPermission(contextClassLoader,
1437                                                    Reflection.getCallerClass());
1438         }
1439         return contextClassLoader;
1440     }
1441 
1442     /**
1443      * Sets the context ClassLoader for this Thread. The context
1444      * ClassLoader can be set when a thread is created, and allows
1445      * the creator of the thread to provide the appropriate class loader,
1446      * through {@code getContextClassLoader}, to code running in the thread
1447      * when loading classes and resources.
1448      *
1449      * <p>If a security manager is present, its {@link
1450      * SecurityManager#checkPermission(java.security.Permission) checkPermission}
1451      * method is invoked with a {@link RuntimePermission RuntimePermission}{@code
1452      * ("setContextClassLoader")} permission to see if setting the context
1453      * ClassLoader is permitted.
1454      *
1455      * @param  cl
1456      *         the context ClassLoader for this Thread, or null  indicating the
1457      *         system class loader (or, failing that, the bootstrap class loader)
1458      *
1459      * @throws  SecurityException
1460      *          if the current thread cannot set the context ClassLoader
1461      *
1462      * @since 1.2
1463      */
1464     public void setContextClassLoader(ClassLoader cl) {
1465         SecurityManager sm = System.getSecurityManager();
1466         if (sm != null) {
1467             sm.checkPermission(new RuntimePermission("setContextClassLoader"));
1468         }
1469         contextClassLoader = cl;
1470     }
1471 
1472     /**
1473      * Returns <tt>true</tt> if and only if the current thread holds the
1474      * monitor lock on the specified object.
1475      *
1476      * <p>This method is designed to allow a program to assert that
1477      * the current thread already holds a specified lock:
1478      * <pre>
1479      *     assert Thread.holdsLock(obj);
1480      * </pre>
1481      *
1482      * @param  obj the object on which to test lock ownership
1483      * @throws NullPointerException if obj is <tt>null</tt>
1484      * @return <tt>true</tt> if the current thread holds the monitor lock on
1485      *         the specified object.
1486      * @since 1.4
1487      */
1488     public static native boolean holdsLock(Object obj);
1489 
1490     private static final StackTraceElement[] EMPTY_STACK_TRACE
1491         = new StackTraceElement[0];
1492 
1493     /**
1494      * Returns an array of stack trace elements representing the stack dump
1495      * of this thread.  This method will return a zero-length array if
1496      * this thread has not started, has started but has not yet been
1497      * scheduled to run by the system, or has terminated.
1498      * If the returned array is of non-zero length then the first element of
1499      * the array represents the top of the stack, which is the most recent
1500      * method invocation in the sequence.  The last element of the array
1501      * represents the bottom of the stack, which is the least recent method
1502      * invocation in the sequence.
1503      *
1504      * <p>If there is a security manager, and this thread is not
1505      * the current thread, then the security manager's
1506      * <tt>checkPermission</tt> method is called with a
1507      * <tt>RuntimePermission("getStackTrace")</tt> permission
1508      * to see if it's ok to get the stack trace.
1509      *
1510      * <p>Some virtual machines may, under some circumstances, omit one
1511      * or more stack frames from the stack trace.  In the extreme case,
1512      * a virtual machine that has no stack trace information concerning
1513      * this thread is permitted to return a zero-length array from this
1514      * method.
1515      *
1516      * @return an array of <tt>StackTraceElement</tt>,
1517      * each represents one stack frame.
1518      *
1519      * @throws SecurityException
1520      *        if a security manager exists and its
1521      *        <tt>checkPermission</tt> method doesn't allow
1522      *        getting the stack trace of thread.
1523      * @see SecurityManager#checkPermission
1524      * @see RuntimePermission
1525      * @see Throwable#getStackTrace
1526      *
1527      * @since 1.5
1528      */
1529     public StackTraceElement[] getStackTrace() {
1530         if (this != Thread.currentThread()) {
1531             // check for getStackTrace permission
1532             SecurityManager security = System.getSecurityManager();
1533             if (security != null) {
1534                 security.checkPermission(
1535                     SecurityConstants.GET_STACK_TRACE_PERMISSION);
1536             }
1537             // optimization so we do not call into the vm for threads that
1538             // have not yet started or have terminated
1539             if (!isAlive()) {
1540                 return EMPTY_STACK_TRACE;
1541             }
1542             StackTraceElement[][] stackTraceArray = dumpThreads(new Thread[] {this});
1543             StackTraceElement[] stackTrace = stackTraceArray[0];
1544             // a thread that was alive during the previous isAlive call may have
1545             // since terminated, therefore not having a stacktrace.
1546             if (stackTrace == null) {
1547                 stackTrace = EMPTY_STACK_TRACE;
1548             }
1549             return stackTrace;
1550         } else {
1551             // Don't need JVM help for current thread
1552             return (new Exception()).getStackTrace();
1553         }
1554     }
1555 
1556     /**
1557      * Returns a map of stack traces for all live threads.
1558      * The map keys are threads and each map value is an array of
1559      * <tt>StackTraceElement</tt> that represents the stack dump
1560      * of the corresponding <tt>Thread</tt>.
1561      * The returned stack traces are in the format specified for
1562      * the {@link #getStackTrace getStackTrace} method.
1563      *
1564      * <p>The threads may be executing while this method is called.
1565      * The stack trace of each thread only represents a snapshot and
1566      * each stack trace may be obtained at different time.  A zero-length
1567      * array will be returned in the map value if the virtual machine has
1568      * no stack trace information about a thread.
1569      *
1570      * <p>If there is a security manager, then the security manager's
1571      * <tt>checkPermission</tt> method is called with a
1572      * <tt>RuntimePermission("getStackTrace")</tt> permission as well as
1573      * <tt>RuntimePermission("modifyThreadGroup")</tt> permission
1574      * to see if it is ok to get the stack trace of all threads.
1575      *
1576      * @return a <tt>Map</tt> from <tt>Thread</tt> to an array of
1577      * <tt>StackTraceElement</tt> that represents the stack trace of
1578      * the corresponding thread.
1579      *
1580      * @throws SecurityException
1581      *        if a security manager exists and its
1582      *        <tt>checkPermission</tt> method doesn't allow
1583      *        getting the stack trace of thread.
1584      * @see #getStackTrace
1585      * @see SecurityManager#checkPermission
1586      * @see RuntimePermission
1587      * @see Throwable#getStackTrace
1588      *
1589      * @since 1.5
1590      */
1591     public static Map<Thread, StackTraceElement[]> getAllStackTraces() {
1592         // check for getStackTrace permission
1593         SecurityManager security = System.getSecurityManager();
1594         if (security != null) {
1595             security.checkPermission(
1596                 SecurityConstants.GET_STACK_TRACE_PERMISSION);
1597             security.checkPermission(
1598                 SecurityConstants.MODIFY_THREADGROUP_PERMISSION);
1599         }
1600 
1601         // Get a snapshot of the list of all threads
1602         Thread[] threads = getThreads();
1603         StackTraceElement[][] traces = dumpThreads(threads);
1604         Map<Thread, StackTraceElement[]> m = new HashMap<>(threads.length);
1605         for (int i = 0; i < threads.length; i++) {
1606             StackTraceElement[] stackTrace = traces[i];
1607             if (stackTrace != null) {
1608                 m.put(threads[i], stackTrace);
1609             }
1610             // else terminated so we don't put it in the map
1611         }
1612         return m;
1613     }
1614 
1615 
1616     private static final RuntimePermission SUBCLASS_IMPLEMENTATION_PERMISSION =
1617                     new RuntimePermission("enableContextClassLoaderOverride");
1618 
1619     /** cache of subclass security audit results */
1620     /* Replace with ConcurrentReferenceHashMap when/if it appears in a future
1621      * release */
1622     private static class Caches {
1623         /** cache of subclass security audit results */
1624         static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
1625             new ConcurrentHashMap<>();
1626 
1627         /** queue for WeakReferences to audited subclasses */
1628         static final ReferenceQueue<Class<?>> subclassAuditsQueue =
1629             new ReferenceQueue<>();
1630     }
1631 
1632     /**
1633      * Verifies that this (possibly subclass) instance can be constructed
1634      * without violating security constraints: the subclass must not override
1635      * security-sensitive non-final methods, or else the
1636      * "enableContextClassLoaderOverride" RuntimePermission is checked.
1637      */
1638     private static boolean isCCLOverridden(Class<?> cl) {
1639         if (cl == Thread.class)
1640             return false;
1641 
1642         processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
1643         WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
1644         Boolean result = Caches.subclassAudits.get(key);
1645         if (result == null) {
1646             result = Boolean.valueOf(auditSubclass(cl));
1647             Caches.subclassAudits.putIfAbsent(key, result);
1648         }
1649 
1650         return result.booleanValue();
1651     }
1652 
1653     /**
1654      * Performs reflective checks on given subclass to verify that it doesn't
1655      * override security-sensitive non-final methods.  Returns true if the
1656      * subclass overrides any of the methods, false otherwise.
1657      */
1658     private static boolean auditSubclass(final Class<?> subcl) {
1659         Boolean result = AccessController.doPrivileged(
1660             new PrivilegedAction<Boolean>() {
1661                 public Boolean run() {
1662                     for (Class<?> cl = subcl;
1663                          cl != Thread.class;
1664                          cl = cl.getSuperclass())
1665                     {
1666                         try {
1667                             cl.getDeclaredMethod("getContextClassLoader", new Class<?>[0]);
1668                             return Boolean.TRUE;
1669                         } catch (NoSuchMethodException ex) {
1670                         }
1671                         try {
1672                             Class<?>[] params = {ClassLoader.class};
1673                             cl.getDeclaredMethod("setContextClassLoader", params);
1674                             return Boolean.TRUE;
1675                         } catch (NoSuchMethodException ex) {
1676                         }
1677                     }
1678                     return Boolean.FALSE;
1679                 }
1680             }
1681         );
1682         return result.booleanValue();
1683     }
1684 
1685     private native static StackTraceElement[][] dumpThreads(Thread[] threads);
1686     private native static Thread[] getThreads();
1687 
1688     /**
1689      * Returns the identifier of this Thread.  The thread ID is a positive
1690      * <tt>long</tt> number generated when this thread was created.
1691      * The thread ID is unique and remains unchanged during its lifetime.
1692      * When a thread is terminated, this thread ID may be reused.
1693      *
1694      * @return this thread's ID.
1695      * @since 1.5
1696      */
1697     public long getId() {
1698         return tid;
1699     }
1700 
1701     /**
1702      * A thread state.  A thread can be in one of the following states:
1703      * <ul>
1704      * <li>{@link #NEW}<br>
1705      *     A thread that has not yet started is in this state.
1706      *     </li>
1707      * <li>{@link #RUNNABLE}<br>
1708      *     A thread executing in the Java virtual machine is in this state.
1709      *     </li>
1710      * <li>{@link #BLOCKED}<br>
1711      *     A thread that is blocked waiting for a monitor lock
1712      *     is in this state.
1713      *     </li>
1714      * <li>{@link #WAITING}<br>
1715      *     A thread that is waiting indefinitely for another thread to
1716      *     perform a particular action is in this state.
1717      *     </li>
1718      * <li>{@link #TIMED_WAITING}<br>
1719      *     A thread that is waiting for another thread to perform an action
1720      *     for up to a specified waiting time is in this state.
1721      *     </li>
1722      * <li>{@link #TERMINATED}<br>
1723      *     A thread that has exited is in this state.
1724      *     </li>
1725      * </ul>
1726      *
1727      * <p>
1728      * A thread can be in only one state at a given point in time.
1729      * These states are virtual machine states which do not reflect
1730      * any operating system thread states.
1731      *
1732      * @since   1.5
1733      * @see #getState
1734      */
1735     public enum State {
1736         /**
1737          * Thread state for a thread which has not yet started.
1738          */
1739         NEW,
1740 
1741         /**
1742          * Thread state for a runnable thread.  A thread in the runnable
1743          * state is executing in the Java virtual machine but it may
1744          * be waiting for other resources from the operating system
1745          * such as processor.
1746          */
1747         RUNNABLE,
1748 
1749         /**
1750          * Thread state for a thread blocked waiting for a monitor lock.
1751          * A thread in the blocked state is waiting for a monitor lock
1752          * to enter a synchronized block/method or
1753          * reenter a synchronized block/method after calling
1754          * {@link Object#wait() Object.wait}.
1755          */
1756         BLOCKED,
1757 
1758         /**
1759          * Thread state for a waiting thread.
1760          * A thread is in the waiting state due to calling one of the
1761          * following methods:
1762          * <ul>
1763          *   <li>{@link Object#wait() Object.wait} with no timeout</li>
1764          *   <li>{@link #join() Thread.join} with no timeout</li>
1765          *   <li>{@link LockSupport#park() LockSupport.park}</li>
1766          * </ul>
1767          *
1768          * <p>A thread in the waiting state is waiting for another thread to
1769          * perform a particular action.
1770          *
1771          * For example, a thread that has called <tt>Object.wait()</tt>
1772          * on an object is waiting for another thread to call
1773          * <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on
1774          * that object. A thread that has called <tt>Thread.join()</tt>
1775          * is waiting for a specified thread to terminate.
1776          */
1777         WAITING,
1778 
1779         /**
1780          * Thread state for a waiting thread with a specified waiting time.
1781          * A thread is in the timed waiting state due to calling one of
1782          * the following methods with a specified positive waiting time:
1783          * <ul>
1784          *   <li>{@link #sleep Thread.sleep}</li>
1785          *   <li>{@link Object#wait(long) Object.wait} with timeout</li>
1786          *   <li>{@link #join(long) Thread.join} with timeout</li>
1787          *   <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
1788          *   <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
1789          * </ul>
1790          */
1791         TIMED_WAITING,
1792 
1793         /**
1794          * Thread state for a terminated thread.
1795          * The thread has completed execution.
1796          */
1797         TERMINATED;
1798     }
1799 
1800     /**
1801      * Returns the state of this thread.
1802      * This method is designed for use in monitoring of the system state,
1803      * not for synchronization control.
1804      *
1805      * @return this thread's state.
1806      * @since 1.5
1807      */
1808     public State getState() {
1809         // get current thread state
1810         return sun.misc.VM.toThreadState(threadStatus);
1811     }
1812 
1813     // Added in JSR-166
1814 
1815     /**
1816      * Interface for handlers invoked when a <tt>Thread</tt> abruptly
1817      * terminates due to an uncaught exception.
1818      * <p>When a thread is about to terminate due to an uncaught exception
1819      * the Java Virtual Machine will query the thread for its
1820      * <tt>UncaughtExceptionHandler</tt> using
1821      * {@link #getUncaughtExceptionHandler} and will invoke the handler's
1822      * <tt>uncaughtException</tt> method, passing the thread and the
1823      * exception as arguments.
1824      * If a thread has not had its <tt>UncaughtExceptionHandler</tt>
1825      * explicitly set, then its <tt>ThreadGroup</tt> object acts as its
1826      * <tt>UncaughtExceptionHandler</tt>. If the <tt>ThreadGroup</tt> object
1827      * has no
1828      * special requirements for dealing with the exception, it can forward
1829      * the invocation to the {@linkplain #getDefaultUncaughtExceptionHandler
1830      * default uncaught exception handler}.
1831      *
1832      * @see #setDefaultUncaughtExceptionHandler
1833      * @see #setUncaughtExceptionHandler
1834      * @see ThreadGroup#uncaughtException
1835      * @since 1.5
1836      */
1837     @FunctionalInterface
1838     public interface UncaughtExceptionHandler {
1839         /**
1840          * Method invoked when the given thread terminates due to the
1841          * given uncaught exception.
1842          * <p>Any exception thrown by this method will be ignored by the
1843          * Java Virtual Machine.
1844          * @param t the thread
1845          * @param e the exception
1846          */
1847         void uncaughtException(Thread t, Throwable e);
1848     }
1849 
1850     // null unless explicitly set
1851     private volatile UncaughtExceptionHandler uncaughtExceptionHandler;
1852 
1853     // null unless explicitly set
1854     private static volatile UncaughtExceptionHandler defaultUncaughtExceptionHandler;
1855 
1856     /**
1857      * Set the default handler invoked when a thread abruptly terminates
1858      * due to an uncaught exception, and no other handler has been defined
1859      * for that thread.
1860      *
1861      * <p>Uncaught exception handling is controlled first by the thread, then
1862      * by the thread's {@link ThreadGroup} object and finally by the default
1863      * uncaught exception handler. If the thread does not have an explicit
1864      * uncaught exception handler set, and the thread's thread group
1865      * (including parent thread groups)  does not specialize its
1866      * <tt>uncaughtException</tt> method, then the default handler's
1867      * <tt>uncaughtException</tt> method will be invoked.
1868      * <p>By setting the default uncaught exception handler, an application
1869      * can change the way in which uncaught exceptions are handled (such as
1870      * logging to a specific device, or file) for those threads that would
1871      * already accept whatever &quot;default&quot; behavior the system
1872      * provided.
1873      *
1874      * <p>Note that the default uncaught exception handler should not usually
1875      * defer to the thread's <tt>ThreadGroup</tt> object, as that could cause
1876      * infinite recursion.
1877      *
1878      * @param eh the object to use as the default uncaught exception handler.
1879      * If <tt>null</tt> then there is no default handler.
1880      *
1881      * @throws SecurityException if a security manager is present and it
1882      *         denies <tt>{@link RuntimePermission}
1883      *         (&quot;setDefaultUncaughtExceptionHandler&quot;)</tt>
1884      *
1885      * @see #setUncaughtExceptionHandler
1886      * @see #getUncaughtExceptionHandler
1887      * @see ThreadGroup#uncaughtException
1888      * @since 1.5
1889      */
1890     public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
1891         SecurityManager sm = System.getSecurityManager();
1892         if (sm != null) {
1893             sm.checkPermission(
1894                 new RuntimePermission("setDefaultUncaughtExceptionHandler")
1895                     );
1896         }
1897 
1898          defaultUncaughtExceptionHandler = eh;
1899      }
1900 
1901     /**
1902      * Returns the default handler invoked when a thread abruptly terminates
1903      * due to an uncaught exception. If the returned value is <tt>null</tt>,
1904      * there is no default.
1905      * @since 1.5
1906      * @see #setDefaultUncaughtExceptionHandler
1907      * @return the default uncaught exception handler for all threads
1908      */
1909     public static UncaughtExceptionHandler getDefaultUncaughtExceptionHandler(){
1910         return defaultUncaughtExceptionHandler;
1911     }
1912 
1913     /**
1914      * Returns the handler invoked when this thread abruptly terminates
1915      * due to an uncaught exception. If this thread has not had an
1916      * uncaught exception handler explicitly set then this thread's
1917      * <tt>ThreadGroup</tt> object is returned, unless this thread
1918      * has terminated, in which case <tt>null</tt> is returned.
1919      * @since 1.5
1920      * @return the uncaught exception handler for this thread
1921      */
1922     public UncaughtExceptionHandler getUncaughtExceptionHandler() {
1923         return uncaughtExceptionHandler != null ?
1924             uncaughtExceptionHandler : group;
1925     }
1926 
1927     /**
1928      * Set the handler invoked when this thread abruptly terminates
1929      * due to an uncaught exception.
1930      * <p>A thread can take full control of how it responds to uncaught
1931      * exceptions by having its uncaught exception handler explicitly set.
1932      * If no such handler is set then the thread's <tt>ThreadGroup</tt>
1933      * object acts as its handler.
1934      * @param eh the object to use as this thread's uncaught exception
1935      * handler. If <tt>null</tt> then this thread has no explicit handler.
1936      * @throws  SecurityException  if the current thread is not allowed to
1937      *          modify this thread.
1938      * @see #setDefaultUncaughtExceptionHandler
1939      * @see ThreadGroup#uncaughtException
1940      * @since 1.5
1941      */
1942     public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh) {
1943         checkAccess();
1944         uncaughtExceptionHandler = eh;
1945     }
1946 
1947     /**
1948      * Dispatch an uncaught exception to the handler. This method is
1949      * intended to be called only by the JVM.
1950      */
1951     private void dispatchUncaughtException(Throwable e) {
1952         getUncaughtExceptionHandler().uncaughtException(this, e);
1953     }
1954 
1955     /**
1956      * Removes from the specified map any keys that have been enqueued
1957      * on the specified reference queue.
1958      */
1959     static void processQueue(ReferenceQueue<Class<?>> queue,
1960                              ConcurrentMap<? extends
1961                              WeakReference<Class<?>>, ?> map)
1962     {
1963         Reference<? extends Class<?>> ref;
1964         while((ref = queue.poll()) != null) {
1965             map.remove(ref);
1966         }
1967     }
1968 
1969     /**
1970      *  Weak key for Class objects.
1971      **/
1972     static class WeakClassKey extends WeakReference<Class<?>> {
1973         /**
1974          * saved value of the referent's identity hash code, to maintain
1975          * a consistent hash code after the referent has been cleared
1976          */
1977         private final int hash;
1978 
1979         /**
1980          * Create a new WeakClassKey to the given object, registered
1981          * with a queue.
1982          */
1983         WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue) {
1984             super(cl, refQueue);
1985             hash = System.identityHashCode(cl);
1986         }
1987 
1988         /**
1989          * Returns the identity hash code of the original referent.
1990          */
1991         @Override
1992         public int hashCode() {
1993             return hash;
1994         }
1995 
1996         /**
1997          * Returns true if the given object is this identical
1998          * WeakClassKey instance, or, if this object's referent has not
1999          * been cleared, if the given object is another WeakClassKey
2000          * instance with the identical non-null referent as this one.
2001          */
2002         @Override
2003         public boolean equals(Object obj) {
2004             if (obj == this)
2005                 return true;
2006 
2007             if (obj instanceof WeakClassKey) {
2008                 Object referent = get();
2009                 return (referent != null) &&
2010                        (referent == ((WeakClassKey) obj).get());
2011             } else {
2012                 return false;
2013             }
2014         }
2015     }
2016 
2017 
2018     // The following three initially uninitialized fields are exclusively
2019     // managed by class java.util.concurrent.ThreadLocalRandom. These
2020     // fields are used to build the high-performance PRNGs in the
2021     // concurrent code, and we can not risk accidental false sharing.
2022     // Hence, the fields are isolated with @Contended.
2023 
2024     /** The current seed for a ThreadLocalRandom */
2025     @sun.misc.Contended("tlr")
2026     long threadLocalRandomSeed;
2027 
2028     /** Probe hash value; nonzero if threadLocalRandomSeed initialized */
2029     @sun.misc.Contended("tlr")
2030     int threadLocalRandomProbe;
2031 
2032     /** Secondary seed isolated from public ThreadLocalRandom sequence */
2033     @sun.misc.Contended("tlr")
2034     int threadLocalRandomSecondarySeed;
2035 
2036     /* Some private helper methods */
2037     private native void setPriority0(int newPriority);
2038     private native void stop0(Object o);
2039     private native void suspend0();
2040     private native void resume0();
2041     private native void interrupt0();
2042     private native void setNativeName(String name);
2043 }
View Code

 

Thread类中start()方法

 1     public synchronized void start() {
 2         /**
 3          * This method is not invoked for the main method thread or "system"
 4          * group threads created/set up by the VM. Any new functionality added
 5          * to this method in the future may have to also be added to the VM.
 6          *
 7          * A zero status value corresponds to state "NEW".
 8          */
 9         if (threadStatus != 0)
10             throw new IllegalThreadStateException();
11 
12         /* Notify the group that this thread is about to be started
13          * so that it can be added to the group's list of threads
14          * and the group's unstarted count can be decremented. */
15         group.add(this);
16 
17         boolean started = false;
18         try {
19             start0();
20             started = true;
21         } finally {
22             try {
23                 if (!started) {
24                     group.threadStartFailed(this);
25                 }
26             } catch (Throwable ignore) {
27                 /* do nothing. If start0 threw a Throwable then
28                   it will be passed up the call stack */
29             }
30         }
31     }

start0()//操作 调用的是底层的start0()操作。start0()会调用当前运行对象的run方法,并作为一个线程启动。

 private native void start0();

 

从源码分析可以看出,Thread类其实也是Runnable的一个实现类。

1 // Thread thread = new ThreadDemo(); 2 // thread.start();//多态,此处会调用父类的start()方法,父类方法会去执行子类的run方法。 3 4 5 RunnableDemo run = new RunnableDemo(); 6 Thread thread = new Thread(run);//创建一个Thread类 7 thread.start();//调用start0() >> 调用Thread类本身的的run方法

然后再来看看我们的问题,是不是和上面的代码很像:

 1         new Thread(new Runnable() {//实现runnable接口  2  3 public void run() {  4 System.out.println("Runnable running..");  5  }  6  7 }) {//继承Thread类,那么在调用start的方法时会去调用Thread的子类的方法(即该代码块中的run方法)。  8  9 public void run() { 10 System.out.println("Thread running.."); 11  }; 12 }.start();