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This article shows you how to use the source code to analyze HashSet, the content is concise and easy to understand, can definitely brighten your eyes, through the detailed introduction of this article, I hope you can get something.

Introduction to HashSet public class HashSet extends AbstractSet implements Set, Cloneable, Serializable {}

HashSet inherits AbstractSet and implements that Set; is a collection without repeating elements implemented by HashMap.

The order of elements is not guaranteed, and null elements are allowed

HashSet implements the Cloneable interface and overrides the clone method, so it can be cloned.

HashSet implements the Serializable interface, so it can be serialized.

The operation of HashSet is not thread safe

Member variable / * specific storage HashSet element HashMap * * / private transient HashMap map;/** because Set only uses HashMap's key, so use PRESENT to populate HashMap's Value * / private static final Object PRESENT = new Object (); the constructor / * * default constructor uses HashMap's default constructor * / public HashSet () {map = new HashMap () } / * * through collection construction HashSet first calculates the size value of the HashMap based on the set size and initializes the HashMap and then adds all the collection elements * * / public HashSet (Collection

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