Java之HashSet

HashSet ：https://blog.fondme.cn/apidoc/jdk-1.8-google/

package learn.java.cn.collection;

import java.util.HashMap;
import java.util.HashSet;

public class MyHashSet {
	
	/*
	 * 	###################
	 * 自己实现HashSet
	 */
		
	
	private static final  Object PRESENT=new Object();
	HashMap map;
	public MyHashSet()
	{
		map=new HashMap();
		
	}
	
	
	public int size()
	{
		return map.size();
	}
	
	
	public void add(Object e)
	{
		map.put(e, PRESENT);
	}
	
	
	public static void main(String[] args) {
		MyHashSet s=new MyHashSet();
		s.add("王尚权");
		s.add("小静");
		s.add(new String("王尚权"));
		System.out.println(s.size());
		
	/*
	 * 	###################
	 * 测试java.util 中封装 的HashSet
	 */
		
		HashSet hs=new HashSet();
		HashSet sh=new HashSet();
		
		hs.add("小静");
		hs.add("王尚权");
		sh.add("李白");
		sh.add("杨幂");
		hs.add(sh);//将sh 对象加入到hs，hs.size()增大1
		System.out.println(hs.contains(sh));//结果为真
		System.out.println(hs.contains("杨幂"));//结果为假
		hs.addAll(sh);//将sh的elements加入到hs,hs.size增大2
		System.out.println(hs.contains("杨幂"));//结果为真
		System.out.println(hs.isEmpty());
		System.out.println(hs.size());
		hs.add("李白");//不可重复性
		System.out.println(hs.size());//
		

		
		
	}
}