删除引用以帮助GC是否是一种很好的做法？ [英] Is it a good practice to remove references to help the GC?

问题描述

我想知道您是否认为将对象的引用（将它们设置为 null ）设置为对象以帮助Java垃圾收集器是一种很好的做法。

例如，假设您有一个包含两个字段的类，其中一个字段非常耗费内存。如果你知道你只需要一个特定的处理，你可以在帮助GC之后立即将它清空。

假设我真的需要这两个字段，而不是只有内部变量，所以 heavyObject1 不能在方法结束时超出范围。

你会这样做吗？作为一般做法吗？

  public class TestClass {
 
 public static Object heavyObject1; 
 public static Object object2; 
 
 private static void action（）{
 object2 = doSomething（heavyObject1）; 
 
 heavyObject1 = null; //这个好吗？ 
} 
} 
  

解决方案

通常这是不需要的。

在以下特定情况下，这是个好主意：

• 该对象很大（即足够大以至于不在乎）


• 您确定不再需要该对象 em>


• 对象不会超出范围（例如，您知道周围的对象不会被垃圾收集）

但是，如果您发现自己处于这种情况下，我怀疑您有设计异味：为什么内部对象有这样的不同封闭对象的范围/生命周期？这让我感到怀疑，因为通常当你用合成建立一个对象图时，你期望合成对象的生命期相似。

I am wondering whether you would consider it a good practice to remove references (setting them to null) to objects in order to help the Java Garbage Collector.

For instance, let's say you have a class with two fields, one of them being very memory-consuming. If you know you only need it for a particular processing, you can null it right after to help the GC.

Assume I really need those two to be fields, and not only internal variables, so heavyObject1 cannot be out of scope at the end of the method.

Would you do this as a general practice?

public class TestClass {

   public static Object heavyObject1;
   public static Object object2;

   private static void action() {
    object2 = doSomething(heavyObject1);

    heavyObject1 = null; //is this good?
   }
}

解决方案

Usually it isn't needed.

It's a good idea in the following specific circumstance:

• The object is large (i.e. large enough for you to care)
• You are sure the object won't be needed again
• The object won't go out of scope otherwise (e.g. you know the surrounding object won't be garbage collected)

However if you find yourself in this situation I suspect you have a design smell anyway: why does the internal object have such a different scope / lifetime from the enclosing object? This makes me suspicious, because usually when you build up an object graph with composition you expect the composed objects to have similar lifetimes.

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