如果实例变量仍然有引用，Java GC是否销毁对象？ [英] Does Java GC destroy objects if instance variables still have reference?

问题描述

我已经在网上阅读了一些Java垃圾收集指南，但是我还是有点不清楚，希望确保我的代码中没有内存泄漏。

Java GC是否收集失去引用的对象，但它的变量仍然有引用？

假设我有SomeObject：

  public class SomeObject {
 public ObjectVar var; 
 $ b $ public SomeObject（）{
 var = new ObjectVar（）; 
 
 
 $ / code $ / pre 
 
 
和我的代码：
 
 
  SomeObject obj1 = new SomeObject（）; 
 SomeObject obj2 = new SomeObject（）; 
 obj2.var = obj1.var; 
 obj1 = null; 
  
所以obj1的var有引用，但obj1不再有任何引用。那么，GC是否会销毁obj1，但保持var还活着？ （我假设如此，只是想确定）。谢谢！
解决方案
这里将会发生什么（见下面的评论）
 
 
  // obj1 and obj1.var get created 
 SomeObject obj1 = new SomeObject（）; 
 // obj2和obj2.var获得创建
 SomeObject obj2 = new SomeObject（）; 
 // old obj2.var成为符合GC 
的条件obj2.var = obj1.var; 
 // obj1变为符合GC 
 obj1 = null; 
  
最后，仍有两个对象没有得到GCd  -   obj2 和前 obj1.var ，现在引用为 obj2.var 。
 
 
 
注意：在 ObjectVar 类的特殊情况下，类是的非静态内部类SomeObject ，保持对 obj1.var 的引用也会保持 obj1 。这是因为在内部， SomeObject.ObjectVar 类有一个类型为 SomeObject 的隐藏变量，它引用内部类。
 
I've read through some of the Java garbage collection guides online, but I'm still a bit unclear and wanted to make sure so that I don't have memory leaks in my code.

Does Java GC collect objects that lost its reference, but its variables still have reference?

So let's say I have SomeObject:
public class SomeObject {
    public ObjectVar var;

    public SomeObject() {
        var = new ObjectVar();
    }
}
And my code:
SomeObject obj1 = new SomeObject();
SomeObject obj2 = new SomeObject();
obj2.var = obj1.var;
obj1 = null;
So obj1's var has reference, but obj1 no longer has any reference. So, will the GC destroy obj1, but keep var alive? (I'm assuming so; just wanted to make sure). Thanks!
解决方案
Here is what is going to happen (see comments below)
// obj1 and obj1.var get created
SomeObject obj1 = new SomeObject();
// obj2 and obj2.var get created
SomeObject obj2 = new SomeObject();
// old obj2.var becomes eligible for GC
obj2.var = obj1.var;
// obj1 becomes eligible for GC
obj1 = null;
In the end, two objects remain that do not get GCd - obj2 and the former obj1.var which is now referenced as obj2.var.

Note: In a special case of ObjectVar class being a non-static inner class of SomeObject, keeping a reference to obj1.var would also keep obj1 around. This is because internally the SomeObject.ObjectVar class has a hidden variable of type SomeObject, which references the outer object of the inner class.

                        
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