HashMap练习（存取对象）

public class Student implements Comparable<Student>{

 private String name;

 private int age;

 Student(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;

 }


 //。。。。。。。。。。。。。。。。。。。。。。。。。。。。。

 public int hashCode(){

return name.hashCode()+age*34;

 }

 public boolean equals(Object obj){

if(!(obj instanceof Student)){

throw new ClassCastException("类型不匹配");

}

Student s=(Student)obj;

return this.name.equals(s.name)&&this.age==s.age;
}
//重写hashCode和equals目的是如果姓名和年龄相同则为同一个人，确定唯一性，若不重写，则比较的是对象的hashCode会认为是不同
 //。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。


 public String toString(){

return name+" :"+age;

 }

 @Override

 public int compareTo(Student s) {

int num=new Integer(this.age).compareTo(new Integer(s.age));

if(num==0){

return this.name.compareTo(s.name);

}


return num;

 }



}
//*****************************************************
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;


 public class MapDemo {
 public static void main(String[] args) {
HashMap<Student,String> hm=new HashMap<Student,String>();
      hm.put(new Student("黎明", 21),"北京");
      hm.put(new Student("小红", 20),"上海");
      hm.put(new Student("小明", 25),"武汉");
      hm.put(new Student("小兰", 20),"南京");
      hm.put(new Student("黎明", 21),"南京");
      
  //第一种取的方式keyset
      Set<Student>   keyset=hm.keySet();
      Iterator<Student> it=keyset.iterator();
      while(it.hasNext()){
      Student stu=it.next();
      String addr=hm.get(stu);
      System.out.println(stu.toString()+"   "+addr); 
      }
      System.out.println("***************************************");   
  //第二种取出方式entrySet
      Set<Map.Entry<Student,String>>  entrySet=hm.entrySet();
      Iterator<Map.Entry<Student,String>> itor=entrySet.iterator();
            while(itor.hasNext()){
             Map.Entry<Student,String> me= itor.next();
             Student stu=me.getKey();
             String addr=me.getValue();
             System.out.println(stu.toString()+"   "+addr); 
            }
 }
 }