HashSet hashCode equals

在使用HashSet 的时候往往需要重写他的equals和hashCode方法，简单记录一下调用过程做个备忘
1.当hashcode不相等时，两个对象则不相等,不调用equals
2.当hashcode相等时，则看两个对象是否equals，即调用equals方法比较

public class Person {

	private String name;
	private int age ;

	public Person(){}

	public Person(String name,int age){
		this.name = name;
		this.age = age;
	}
	
	@Override
	public int hashCode() {
		int flag = (int)(Math.random()*100);
		System.out.println("hashCode : " + flag + "(" + this.name + " : " + this.age +")");
		return flag;
	}

	@Override
	public boolean equals(Object obj) {
		if(obj instanceof Person){
			Person p = (Person)obj;
			if(this.name.equals(p.name) && this.age == p.age) {
				System.out.println("equals : true");
				return true;
			}else{
				System.out.println("equals : false");
				return false;
			}
		}
		System.out.println("equals : false");
		return false;
	}
}

	@Test
	public void test(){
		Person p1 = new Person("tom",22);
		Person p2 = new Person("tom",22);
		Person p3 = new Person("jack",22);

		boolean result = p1.equals(p2);
		System.out.println(result);
		System.out.println("========================");
		HashSet<Person> set = new HashSet<Person>();
		set.add(p1);
		System.out.println("========================");
		set.add(p2);
		System.out.println("========================");
		set.add(p3);
		System.out.println("set size : " + set.size());
		System.out.println("========================");

		Iterator<Person> its = set.iterator();

		while(its.hasNext()){
			Person p = its.next();
			System.out.println(p.getName() + " : " + p.getAge());
		}

	}
/*
equals : true
true
========================
hashCode : 23(tom : 22)
========================
hashCode : 9(tom : 22)
========================
hashCode : 89(jack : 22)
set size : 3
========================
tom : 22
tom : 22
jack : 22

*/