Java中this的用法及在构造器中调用构造器

package object;

public class E08_StaticTest {
  int petalCount = 0;
  String s = "initial value";
//(1) 
  E08_StaticTest(int petals) {    petalCount = petals;
    System.out.println("Constructor w/ int arg only, petalCount= "
      + petalCount);
  }
//(2)
  E08_StaticTest(String ss) {    System.out.println("Constructor w/ String arg only, s = " + ss);
    s = ss;
  }
//(3)
  E08_StaticTest(String s, int petals) {    this(petals);
//!    this(s); // Can't call two!
    this.s = s; // Another use of "this"
    System.out.println("String & int args");
  }
//(4)
  E08_StaticTest() {    this("hi", 47);
    System.out.println("default constructor (no args)");
  }
  void printPetalCount() {
//! this(11); // Not inside non-constructor!
    System.out.println("petalCount = " + petalCount + " s = "+ s);
  }
  public static void main(String[] args) {
    E08_StaticTest x = new E08_StaticTest();
    x.printPetalCount();
  }
} /* Output:
Constructor w/ int arg only, petalCount= 47
String & int args
default constructor (no args)
petalCount = 47 s = hi
*///:~

注意：this本身表示对当前对象的引用。

刚开始看这段代码时，没怎么看明白，本以为会直接输出最后两行，没搞懂Constructor w/ int arg only, petalCount= 47；String & int args这两行为什么会输出。后来才明白其原因，

其执行顺序为： E08_StaticTest x = new E08_StaticTest();其后执行（4）的this语句->（3）的this语句->（1）确认int类型为47，输出print->（3）的剩下语句->（4）的剩下语句。这样输出结果就和程序设计的一一对应了。原因：如果构造器的第一个语句形如this（...）这个构造器将调用同一个类的另一个构造器。