Java开发网 - 【求助】关于垃圾收集的一个疑惑

Topic: 【求助】关于垃圾收集的一个疑惑

1.【求助】关于垃圾收集的一个疑惑

Posted by: Starcraft
Posted on: 2003-12-09 11:08

class TestA
{
  TestB b;
  TestA()
  {
    b = new TestB(this);
  }
}

class TestB
{
  TestA a;
  TestB(TestA a)
  {
    this.a = a;
  }
}

class TestAll
{
  public static void main (String args[])
  {
    new TestAll().makeThings(); //line15
    // ...code continues on
  }
  
  void makeThings()
  {
    TestA test = new TestA();
  }
}

Which two statements are true after line 15, before main completes? (A. Line 15 causes a stack overflow.
B. An exception is thrown at runtime.
C. The object referenced by a is eligible for garbage collection.
D. The object referenced by b is eligible for garbage collection.
E. The object referenced by a is not eligible for garbage collection.
F. The object referenced by b is not eligible for garbage collection.

相关的解释：
This is a typical example of the island of isolation. On line 15, the two objects TestA and
TestB have a reference to one an other. Therefore, the correct answers are C. and D. A key
point to remember is that an object that is referenced by another object can be eligible for
garbage collection if the two objects form an island of isolated objects.

2.Re:【求助】关于垃圾收集的一个疑惑 [Re: Starcraft]

Copy to clipboard

Posted by: Starcraft
Posted on: 2003-12-09 11:13

在方法本地创建的对象当方法返回时就符合垃圾收集的条件，除非它被导出到方法以外(即它被返回或者作为异常抛出)。所以a和b都满足回收的条件，所以是CD，不知道这样理解是否正确。

对于本题一知半解，特别搞不太清楚他那些红色的内容到底是什么意思。谁能帮助解释一下么？

3.Re:【求助】关于垃圾收集的一个疑惑 [Re: Starcraft]	Copy to clipboard
Posted by: rostone Posted on: 2003-12-09 13:59 把main()看成一个root, 从root开始trace不到的对象都eligible for garbage collection.

4.Re:【求助】关于垃圾收集的一个疑惑 [Re: Starcraft]	Copy to clipboard
Posted by: dingligang Posted on: 2003-12-10 20:53 代码是不是有语法问题啊？测试一下代码标记