JAVA equals方法重写时要重写hashCode方法

package test;

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

/** 
 * @author [e-mail]
 */
public class Test1
{
	
	public static void main(String[] args) {
		Set<Student> set = new HashSet<Student>();
		Student s1 = new Student("ZhangSan", 13);
		Student s2 = new Student("ZhangSan", 13);
		System.out.println(s1.hashCode());
		System.out.println(s2.hashCode());
		set.add(s1);
		set.add(s2);
		System.out.println(set);
		System.out.println(s1.equals(s2));
	}
	
}

class Student {
	private String name;
	private Integer age;
	public Student(String name, Integer age) {
		this.name = name;
		this.age = age;
	}
	
	public void setName(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}
	
	public Integer getAge() {
		return age;
	}

	public void setAge(Integer age) {
		this.age = age;
	}

	public String toString() {
		return name + "'s age is " + String.valueOf(age);
	}
	
	public boolean equals(Object other) {
		if(this == other)
			return true;
		if(other == null)
			return false;
		if(!(other instanceof Student))
			return false;
		
		final Student stu = (Student)other;
		if(!getName().equals(stu.getName())) 
			return false;
		if(!getAge().equals(stu.getAge()))
			return false;
		return true;
	}
	
	public int hashCode() {
		int result = getName().hashCode();
		result = 29*result + getAge().hashCode();
		return result;
	}
	
}

   在重写equals方法的时候一定要重写hashCode()方法