HashSet解析

运用HashSet存储自定义对象
         ——Person必须重写HashCode()方法和equal()方法

public class Person {
	private String name;
	private int 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;
	}
	public Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}
	public Person() {
		super();
	}
	
	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}
	//Person必须重写HashCode()方法和equal()方法
	@Override
	public int hashCode() {
		System.out.println("Person.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) {
		System.out.println("Person.equals()");
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Person other = (Person) 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;
	}
}

public class TestHashSet {
	public static void main(String[] args) {
		//HashSet底层数据结构使用的是哈希表，主结构是数组   +链表
		HashSet hs = new HashSet();
		hs.add("word");
		Person p1 = new Person("张三",25);
		Person p2 = new Person("李四",25);
		Person p3 = new Person("王二麻子",25);
		Person p4 = new Person("张三",25);
		hs.add(p1);
		hs.add(p2);
		hs.add(p3);
		hs.add(p4);
		Iterator it = hs.iterator();
		while(it.hasNext()) { 
			System.out.println(it.next());
		}	
	}
}