我一直在试图理解不同参考文献之间的差异，但这一理论并没有激发出任何想法让我将其形象化。

有人能简要解释一下不同的参考资料吗？

每种方法都有一个更好的例子。

关于这个主题的另一篇好文章：Java参考对象< Sub >或我如何学会用简单的图表来防止烦恼和爱

提取物：

As you might guess, adding three new optional states to the object life-cycle diagram makes for a mess.
Although the documentation indicates a logical progression from strongly reachable through soft, weak, and phantom, to reclaimed, the actual progression depends on what reference objects your program creates.
If you create a WeakReference but don't create a SoftReference, then an object progresses directly from strongly-reachable to weakly-reachable to finalized to collected. object life-cycle, with reference objects

同样重要的是要记住，并不是所有的对象都与引用对象相关联——事实上，它们应该很少。引用对象是一个间接层：您通过引用对象到达引用对象，显然您不希望在整个代码中使用该间接层。实际上，大多数程序将使用引用对象来访问程序创建的相对较少的对象。

参考文献和参考文献

引用对象提供了程序代码和其他对象(称为引用)之间的间接层。每个引用对象围绕其引用构造，并提供一个get()方法来访问引用。创建引用后，不能更改其引用。一旦收集了引用，get()方法将返回空值。应用程序代码、软/弱引用和引用之间的关系

更多的例子：Java编程：引用的包

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• Case 1: This is the regular case where Object is said to be strongly reachable.

• Case 2: There are two paths to Object, so the strongest one is chosen, which is the one with the strong reference hence the object is strongly reachable.

• Case 3: Once again there are two paths to the Object, the strongest one is the Weak Reference (since the other one is a Phantom Reference), so the object is said to be weakly reachable.

• Case 4: There is only one path and the weakest link is a weak reference, so the object is weakly reachable.

• Case 5: Only one path and the weakest link is the phantom reference hence the object is phantomly reachable.

• Case 6: There are now two paths and the strongest path is the one with a soft reference, so the object is now said to be softly reachable.

一篇解释这些引用类型的文章(包括示例)：http://weblogs.java.net/blog/enicholas/archive/2006/05/understanding_w.html

有一个非常简单的规则：

• 强引用对象是标准的代码位，如Object a = new Object()。只要引用(上面的a是"可访问的"，被引用对象就不会是垃圾。因此，任何没有可到达的强引用的东西都可以被视为垃圾。

然后我们来看看非强引用类型：

• 弱引用对象可能会在它们符合GC(并且清除WeakReference)的条件时被JVM收集。弱引用a看起来像new WeakReference