Collection、Set、List接口都属于单值的操作，即：每次只能操作一个对象，而Map与它们不同的是，每次操作的是一对对象，即二元偶对象，Map中的每个元素都使用key à value的形式存储在集合之中

package com.pb.demo2;public class Person {private String name;private int age;public Person() {}public Person(String name, int age) {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;
}}

package com.pb.demo2;import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;import com.pb.demo1.Person;public class MapTest {public static void main(String[] args) {/** 1.创建多个Person对象并赋值*/Person p1 = new Person("张三",21);Person p2 = new Person("李四",22);Person p3 = new Person("王五",23);Person p4 = new Person("赵六",24);Person p5 = new Person("钱七",25);//2.创建保存键--值对的集合对象Map<String,Person> perMap=new HashMap<String,Person>();//3.使用put将英文名与对象按照键-值对的方式在座存储在HashMap中perMap.put("Denny", p1);perMap.put("Jony", p2);perMap.put("Rose", p3);perMap.put("Kitter", p4);perMap.put("Boby", p5);//4.打印键集System.out.println("++++++++打印键集+++++++++");System.out.println(perMap.keySet());//5.打印值集System.out.println("=========打印值集=======");System.out.println(perMap.values());//6.打印键-值对集合System.out.println("=========打印键-值对集合=======");System.out.println(perMap);//7.判断是否存在"Denny"这个键if(perMap.containsKey("Denny")){//8.如果存在，根据键获取相应的值Person p =perMap.get("Denny");System.out.println("姓名:  "+p.getName());System.out.println("年龄: "+p.getAge());}System.out.println("=======遍历HashMap=======");//遍历HashMap//首先遍历key集合,keySet方法返回的是Set集合Set<String> keySet=perMap.keySet();Iterator<String> iterator=keySet.iterator();while(iterator.hasNext()){String key=iterator.next();System.out.print("英文名:"+key);//根据key值取出值Person p =perMap.get(key);System.out.print("\t姓名:  "+p.getName());System.out.println("\t年龄: "+p.getAge());}}}