Simple analysis of the source code of Set in Java

This article brings you a simple analysis of the source code of Set in Java. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

The Set interface inherits the collection interface, and the methods inside all exist in the collection.

The main implementation classes of Set are: HashSet, TreeSet

HashSet source code

//HashSet的继承关系
public class HashSet<E>    
extends AbstractSet<E>    
implements Set<E>, Cloneable, java.io.Serializable

//由此可以看出hashSet底层实现是用HashMap
private transient HashMap<E,Object> map;
public HashSet() {
        map = new HashMap<>();
    }

Through the following method, we can see that the implementation method of HashSet is the map operation

//遍历    
    public Iterator<E> iterator() {
           return map.keySet().iterator();
    }
    //计算长度
    public int size() {
        return map.size();
    }
    //判断是否为空
    public boolean isEmpty() {
        return map.isEmpty();
    }
    //添加
     public boolean add(E e) {
        return map.put(e, PRESENT)==null;
    }

TreeSet source code

//TreeSet的继承关系
public class TreeSet<E> extends AbstractSet<E>    
implements NavigableSet<E>, Cloneable, java.io.Serializable

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