重写equals方法后，虽然不显示重复的元素了，但是查找还是能找到，为什么？

相关截图：

问题描述：

如果，s3和s4是相同元素，则应该只添加一个，另一个应该是查不到的状态啊，为什么在这里是可以查到的呢？

相关代码：

package com.demon.modle;

public class student {
	private int stuId;
	private String name;
	private float score;

	public student(int stuId, String name, float score) {
		setStuId(stuId);
		setName(name);
		setScore(score);
	}

	public int getStuId() {
		return stuId;
	}

	public void setStuId(int stuId) {
		this.stuId = stuId;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public float getScore() {
		return score;
	}

	public void setScore(float score) {
		this.score = score;
	}

	@Override
	public String toString() {
		return "student [stuId=" + stuId + ", name=" + name + ", score=" + score + "]";
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		result = prime * result + Float.floatToIntBits(score);
		result = prime * result + stuId;
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj.getClass() == student.class) {
			student stu = (student) obj;
			return (stu.getName().equals(name) )&& stu.getScore() == score && stu.getStuId() == stuId;
		}
		return false;

	}

}

相关代码：

​package com.demon.modle;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
public class test {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		student s = new student(1,"张三",65);
		student s2 = new student(2,"李四",87);
		student s3 = new student(3,"王五",95);
		student s4 = new student(3,"王五",95);

		Set set = new HashSet();
		set.add(s);
		set.add(s2);
		set.add(s3);
		set.add(s4);

		Iterator it = set.iterator();
		while(it.hasNext()) {
			System.out.println(it.next());
		}

		System.out.println("添加重复元素后查找：");
		if(set.contains(s4)) {
			System.out.println("包含实例s4");
			System.out.println(s4);
		}else {
			System.out.println("不包含");
			System.out.println("s3："+s3);
		}

	}
}