在 Java 中导致内存泄漏的最简单方法 [英] Easiest way to cause a memory leak in Java

问题描述

<块引用>

可能的重复:
使用 Java 造成内存泄漏

导致 Java 内存泄漏的最简单方法是什么?

解决方案

你不能真正泄漏内存"在 Java 中，除非您:

• 实习生字符串
• 生成类
• 由 JNI
调用的本机代码中的内存泄漏
• 将您不想要的东西放在被遗忘或晦涩的地方.

我认为您对最后一个案例感兴趣.常见的场景有:

• 监听器，尤其是内部类
• 缓存.

一个很好的例子是:

• 构建一个可以启动无限数量的模态窗口的 Swing GUI；
• 让模态窗口在初始化期间做这样的事情:<代码><预>StaticGuiHelper.getMainApplicationFrame().getOneOfTheButtons().addActionListener(new ActionListener(){public void actionPerformed(ActionEvent e){//没做什么...}})

注册的动作什么都不做，但它会导致模态窗口永远留在内存中，即使在关闭之后，导致泄漏——因为监听器永远不会被取消注册，并且每个匿名内部类对象都持有一个引用(不可见)到它的外部对象.更重要的是 - 从模态窗口引用的任何对象也有可能泄漏.

这就是 EventBus 等库默认使用弱引用的原因.

除了监听器，其他典型的例子是缓存，但我想不出一个很好的例子.

Possible Duplicate:
Creating a memory leak with Java

What's the easiest way to cause a Java memory leak?

解决方案

You cannot really "leak memory" in Java unless you:

• intern strings
• generate classes
• leak memory in the native code called by JNI
• keep references to things that you do not want in some forgotten or obscure place.

I take it that you are interested in the last case. The common scenarios are:

• listeners, especially done with inner classes
• caches.

A nice example would be to:

• build a Swing GUI that launches a potentially unlimited number of modal windows;
• have the modal window do something like this during its initialization:

  StaticGuiHelper.getMainApplicationFrame().getOneOfTheButtons().addActionListener(new ActionListener(){
  public void actionPerformed(ActionEvent e){
  // do nothing...
  }
  })
  

The registered action does nothing, but it will cause the modal window to linger in memory forever, even after closing, causing a leak - since the listeners are never unregistered, and each anonymous inner class object holds a reference (invisible) to its outer object. What's more - any object referenced from the modal windows have a chance of leaking too.

This is why libraries such as EventBus use weak references by default.

Apart from listeners, other typical examples are caches, but I cannot think of a nice example.

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