HashMap中put函数的返回值

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put函数返回值是键值对后面的那个value值

今天写程序看到

statue=hashmap.put(x,y);

我一开始以为返回值是1或者0

后来仔细看一下api文档原来不是如此。。

不知道设计者的意图是什么？？？

public V put(K key,    V value)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.

Specified by:: put in interface Map<K,V>
Overrides:: put in class AbstractMap<K,V>
Parameters:: key - key with which the specified value is to be associated; value - value to be associated with the specified key
Returns:: the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key.)

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