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This article mainly explains the "HashMap storage custom classes, need to rewrite custom classes of which methods", the article explains the content is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in-depth, together to study and learn "HashMap storage custom classes, need to rewrite custom classes of which methods" it!

Override the hashcode and equals methods.

The hashCode () method is a local native method that returns the memory address of the object stored in the object reference, while the equals method is compared with = =, which is also the memory address of the object.

Key in HashMap is compared in this way, first find out the hashcode () of Key, compare whether it is equal, compare equals (), if they are equal, they are considered to be equal. If you only override hashcode () and not equals (), their memory addresses are compared when equals () is called. So both methods must be rewritten together.

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