HashSet的特殊特性

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HashSet除了在元素的存储上是无序的以外，还是不能够存储重复的元素。

HashSet如何判断元素是否重复呢？是根据元素继承的两个方法来判断，hashCode和equals，当存储元素时，首先判断要存入的元素和已存在的元素的哈希值是否相同，若不相同存入，若相同则利用equals判断两个元素是否相同，若不相同，则存入，若相同则放弃。而hashCode和equlas是在存入元素自动调用的。

一下继续利用Person类举例

import java.util.*;

class Person

{

????private String name; //姓名

????private int age;????//年龄

?

????public Person(String name, int age)

????{

????????this.name = name;

????????this.age = age;

????}

????//用于生成自定义的哈希值

????public int hashCode()

????{

????????return this.name.hashCode()+this.age*36;

????}

????//自己定义比较规则，与ArrayList相同

????public boolean equals(Object obj)

????{

????????if(!(obj instanceof Person))

????????????return false;

????????Person p = (Person)obj;

????????return p.getName().equals(this.getName()) && (p.getAge() == this.getAge());

????}

????public String getName()

????{

????????return this.name;

????}

?

????public int getAge()

????{

????????return this.age;

????}

?

????public void setName(String name)

????{

????????this.name = name;

????}

?

????public void setAge(int age)

????{

????????this.age = age;

????}

}

?

public class Test

{

????public static void main(String[] args)

????{

????????HashSet<Person> hs = new HashSet<>();

?

????????hs.add(new Person("zhangsan", 23));

????????hs.add(new Person("lisi", 23));

????????hs.add(new Person("zhangsan", 23));

????????hs.add(new Person("wangwu", 35));

????????hs.add(new Person("zhangsan", 67));

????????hs.add(new Person("zhaoliu", 45));

?

????????Iterator<Person> it = hs.iterator();

?

????????while(it.hasNext())

????????{

????????????Person p = it.next();

????????????System.out.println(p.getName()+"...."+p.getAge());

????????}

????}

}

HashSet的特殊特性

标签：java   ar   on   c   amp   ad   new   r   as   

原文地址：http://www.cnblogs.com/fantasy01/p/3972746.html