为什么往重写了equals和hashCode方法的Set集合里成功添加了相同的元素？

Question

package pace;

import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;

import java.util.HashSet;
import java.util.Iterator;

class testHas{
    public final int count;
    public testHas(int count){
        this.count = count;
    }
    public String toString(){
        return "testHas[count: " + count + "]";
    }
    @Override
    public int hashCode(){
        return this.count;
    }
    @Override
    public boolean equals(Object obj){
        if(this == obj){   // 判断是否为同一个对象，自己与自己比较
            return true;
        }
        else if( obj != null && obj.getClass() == testHas.class){  // 判断两个对象是否出自同一个（运行时）类
            testHas temp = (testHas) obj; // 强制类型转换
            return this.toString() == temp.toString();
        }
        return false;
    }
}
public class HashSetclass {
    public static void main(String[] args){
        HashSet set = new HashSet();
        set.add(new testHas(1));
        set.add(new testHas(2));
        set.add(new testHas(3));
        set.add(new testHas(4));
        set.add(new testHas(4));
        System.out.println(set);  // [testHas[count: 1], testHas[count: 2], testHas[count: 3], testHas[count: 4], testHas[count: 4]
    }
}

如图，我重复向Set集合里add了相同count变量的testHas对象，然后输出结果里还存在它，为什么？刚学，求解答

// 结果
[testHas[count: 1], testHas[count: 2], testHas[count: 3], testHas[count: 4], testHas[count: 4]

Answer 1