7-9 HashSet 重写相应方法

import java.util.*;
class Student{
	String id;
	String name;
	public Student(String id,String name) {
		this.id=id;
		this.name=name;
	}
	public String toString() {
		return id+":"+name;
	}
	//重写hashCode()方法
	public int hashCode() {
		return id.hashCode() ;//返回id属性的哈希值
	}
	//重写equals()方法
	public boolean equals(Object obj) {
		if(this==obj) {
			return true;//判断是否为同一个对象
		}
		if(!(obj instanceof Student)) {//判断对象是否为Student类型
			return false;
		}
		Student stu=(Student)obj;
		boolean b=this.id.equals(stu.id);
		return b;
	}
}
public class Example {
public static void main(String[]args) {
	HashSet hset=new HashSet();
	hset.add(new Student("1","张三"));
	hset.add(new Student("2","李四"));
	hset.add(new Student("2","李四"));
		System.out.println(hset);
}
}

运行结果：

[1:张三, 2:李四]