Java集合框架——LinkedHashMap集合

一、Map集合的继承体系

• Map
  • TreeMap
  • HashMap
    • LinkedHashMap

二、数据结构

• 链表 + 哈希表
• 链表：保证数据是有序的，添加顺序和迭代顺序是一致的
• 哈希表：保证键是唯一的（去重的作用）

三、代码演示

• LinkedHashMap集合与HashMap集合的区别在于LinkedHashMap集合传入和遍历出的顺序是相同

//Person.java
package com.map.demo2;

public class Person {
	private String name;
	private int age;
	
	public Person() {
		super();
	}

	public Person(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 "Person [name=" + name + ", age=" + age + "]";
	}

	@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;
		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;
	}
}

//LinkedHashMapTest.java
package com.map.demo3;

import java.util.LinkedHashMap;
import java.util.Set;

public class LinkedHashMapTest {
	public static void main(String[] args) {
		LinkedHashMap<String, Person> map = new LinkedHashMap<String, Person>();
		
		Person p1 = new Person("张三", 18);
		Person p2 = new Person("李四", 19);
		Person p3 = new Person("王五", 20);
		Person p4 = new Person("赵六", 21);
		Person p5 = new Person("马七", 22);
		
		map.put("001", p1);
		map.put("002", p2);
		map.put("003", p3);
		map.put("004", p4);
		map.put("005", p5);
		
		Set<String> keySet = map.keySet();
		for (String key : keySet) {
			Person person = map.get(key);
			System.out.println(key + "-----" + person);
		}
	}
}

• 执行结果：
  001-----Person [name=张三, age=18]
  002-----Person [name=李四, age=19]
  003-----Person [name=王五, age=20]
  004-----Person [name=赵六, age=21]
  005-----Person [name=马七, age=22]