手工实现hashset

package cn.study.lu.four;

import java.util.*;

/**
* 手工实现hashmap,加深理解底层原理
* @author Administrator
*
*/
public class MyHashSet {
HashMap map;
private static final Object PRESENT = new Object();



public MyHashSet() {
map = new HashMap();
}

public void put(Object o) { map.put(o,PRESENT); } public int size() { return map.size(); } @Override public String toString() { StringBuilder sb = new StringBuilder(); sb.append("["); for(Object key: map.keySet()) { sb.append(key+","); } sb.setCharAt(sb.length()-1,‘]‘); return sb.toString(); } public static void main(String[] args) { MyHashSet set = new MyHashSet(); set.put("aaa"); set.put("bbb"); set.put("ccc"); set.put("ddd"); System.out.println(set); }}