java垃圾收集和空引用 [英] java garbage collection and null reference

问题描述

  class CardBoard {
 Short story = 200 ; 
 CardBoard去（CardBoard cb）{
 cb = null; 
 return cb; 
 
 public static void main（String [] args）{
 CardBoard c1 = new CardBoard（）; 
 CardBoard c2 =新的CardBoard（）; 
 CardBoard c3 = c1.go（c2）; 
 c1 = null; 
 //做东西
}} 
  

//当达到doStuff时，有多少对象符合GC的要求？

正确答案是2，意思是 c1 及其故事 object。

当行// doStuff到达时，c3也是null。为什么它不符合GC的标准？

解决方案

c3是一个带有null引用的本地句柄，它没有指向hever指向）分配的对象。因此，GC没有任何问题。

In my studying for OCJP I came across the following question:

class CardBoard {
           Short story = 200;
           CardBoard go(CardBoard cb) {
                cb = null;
                return cb;
           }
           public static void main(String[] args) {
             CardBoard c1 = new CardBoard();
             CardBoard c2 = new CardBoard();
             CardBoard c3 = c1.go(c2);
             c1 = null;
            // do Stuff 
}}

When //doStuff is reached, how many objects are eligible for GC?
The correct answer is 2, meaning c1 and its story object.

When line //doStuff is reached, c3 is also null. Why isn't it eligible for GC too?

解决方案

c3 is a local handle with a null reference, it does not point (and hever has pointed) to an allocated object. Therefore there's nothing to GC.

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