在java Hashmap中将自己的类设置为键 [英] Setting own class as key in java Hashmap

问题描述

我有一个类，我想将其设置为 HashMap 中的键.我已经为该类实现了 compareTo 方法.但是当我这样做时:

<上一页>map.put(new MyKey(dummyArguements) , dummyValue );System.out.println(map.get( new MyKey(dummyArguements) ) );

我得到空值.所以这意味着 hashmap 无法识别这两个键(用于 get 和 put 调用)是相同的.

有人可以帮我吗?

解决方案

需要实现hashCode()和equals().compareTo() 对于有序的地图/集合是额外需要的.

有关详细信息，请参阅此问题.

I have a class which I want to set up as keys in HashMap. I already have implemented the compareTo method for that class. But still when I do:

map.put(new MyKey(dummyArguements) , dummyValue );
System.out.println(map.get( new MyKey(dummyArguements) ) );

I get null. So that means hashmap is not able to identify that the two keys (for get & put call) are same.

Could someone help me here please ?

解决方案

You need to implement hashCode() and equals(). compareTo() is additionally required for sorted map/set.

See this question for details.

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