finally可以分两方面理解
1.执行时机问题。finally总会执行(除非是System.exit()),正常情况下在try后执行,抛异常时在catche后面执行
2.返回值问题。可以认为try(或者catch)中的return语句的返回值放入线程栈的顶部:如果返回值是基本类型则顶部存放的就是值,如果返回值是引用类型,则顶部存放的是引用。finally中的return语句可以修改引用所对应的对象,无法修改基本类型。但不管是基本类型还是引用类型,都可以被finally返回的“具体值”具体值覆盖
3.不建议在finally中使用return语句,如果有,eclipse会warning“finally block does not complete normally”
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package com.ljn. base ;
/** * @author lijinnan
* @date:2014-1-22
*/
public class FinallyTest {
public static void main(String[] args) {
System. out .println(test());
System. out .println(testPrimitive());
}
public static Student test() {
Student result = new Student( "Tom" , 0);
try {
result.setAge(1);
return result;
} catch (Exception e) {
result.setAge(2);
return result;
} finally {
result.setAge(3); //引用类型的返回值,可被修改
//return new Student("Kobe", 33); //可以被“具体值”覆盖
}
}
public static int testPrimitive() {
int x = 0;
try {
x = 1;
return x;
} catch (Exception e) {
x = 2;
return x;
} finally {
x = 3; //基本类型的返回值,不可被修改
//return x; //可以被“具体值”覆盖
}
}
private static class Student {
private String name;
private int age;
public Student(String name, int age) {
this .name = name;
this .age = age;
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + "]" ;
}
public void setAge( int age) {
this .age = age;
}
}
} |