java題求解（為什麼size為3呢）

package com;

import java.util.HashSet;

public class WrappedString {

private String s;

public WrappedString(String s) {

this.s = s;

}

public static void main(String[] args) {

HashSeths = new HashSet();

WrappedString ws1 = new WrappedString("a");

WrappedString ws2 = new WrappedString("a");

String s1 = new String("a");

String s2 = new String("a");

hs.add(ws1);

hs.add(ws2);

hs.add(s1);

hs.add(s2);

System.out.println(hs.size());

}

}