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Static nested class in Java, why?

我在JDK HashTable读到源代码,下面有一些代码片段:

** 易燃碰撞清单。 *

private static class Entry<K,V> implements Map.Entry<K,V> {
    int hash;
    K key;
    V value;
    Entry<K,V> next;
    ...
} //end of Entry<K,V>

I know the Entry here is a private inner class, but it s also a defined static class; my concern is, it isn t enough to just define it as private inner class? What s the main usage here to define it as a static class?

任何指南或答复均不胜感激。

Answer 1

它是stistic ,因此其实例不包含外类包含实例的引用。

map.Entry 用于通过地图元素循环。它无需引用包含的地图, 因为它不需要进入地图的私人字段。因此, 宣布它为非静态只会使用额外空间并削弱封装。

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