package com.runoob.test;

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

public class HashSetTest {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		/*
		 * 练习：往HashSet中存储学生对象(姓名，年龄) 同姓名，同年龄视为一个人，不存
		 * 1.描述学生
		 * 2.定义容器
		 * 3.将学生对象存储到容器中
		 * 
		 * 
		 * 发现存储了同姓名童年里的学生是可以的
		 * 原因是每一次存储学生对象时，都先调用hashCode方法获取哈希值
		 * 但是调用的是Object类中的hashCode，所以不同的对象，哈希值也不同
		 * 这就是同姓名同年龄存入的原因
		 * 
		 * 解决：
		 * 需要根据学生对象自身的特点来定义哈希值
		 * 所以就需要覆盖hashCode方法
		 */
		
		//1.创建容器对象
		Set set = new HashSet();
		
		//2.存储学生对象
		set.add(new Student("xiaoqiang",21));
		set.add(new Student("wangcai",27));
		set.add(new Student("xiaoming",22));
		set.add(new Student("xiaoqi",23));
		set.add(new Student("xiaoming",22));
		set.add(new Student("xiaoqi",23));
		
		//3.获取所有学生
		for (Iterator it = set.iterator(); it.hasNext();) {
			Student stu = (Student) it.next();
			System.out.println(stu.getName()+"::"+stu.getAge());
			
		}
	}

}

package com.runoob.test;

  class Student {
	
	private String name;
	private int age;
	
	
	public Student() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Student(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "Student [name=" + name + ", age=" + age + "]";
	}
	
	/*shift+alt+s 快捷键出来的  
	 * *(non-Javadoc)
	 * @see java.lang.Object#hashCode()
	 
	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + age;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}
	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Student other = (Student) obj;
		if (age != other.age)
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}*/

//哈希值冲突了 需要判断内容 equlas 自己写的
	
//自定义重写hashCode 和equals 方法
	public int hashCode(){
		final int NUMBER=37;
		return name.hashCode()+age*NUMBER;

	}
	
	public boolean equals(Object obj){
		
		//System.out.println(this+"vs"+obj);
		if(this==obj){
			return true;
		}
		
		if(!(obj instanceof Student)){
			throw new ClassCastException("类型错误");
		}
		
		Student stu =(Student)obj;
		return this.name.equals(stu.name)&&this.age==stu.age;
		
	
	}
	
	
}