Map使用的小練習

import java.util.*;
class Student implements Comparable<Student>
{
    private String name;
    private int age;
    Student(String name,int age){
        this.name=name;
        this.age=age;
    }
    /*因爲hashset存儲時需要調用hashCode,equals方法，
    * hashcode通常需要被複寫，默認的hashCode方法是根據地址值進行比較的*/
    public int hashCode(){
        return name.hashCode()+age*34;
    }
    public boolean equals(Object obj){
        if(!(obj instanceof Student)){
            return false;
        }
        Student s = (Student)obj;
        return this.name.equals(s.name)&&this.age==s.age;
    }
    public String getName(){
        return name;
    }
    public int getAge(){
        return age;
    }
    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);          //年齡相同，比較姓名
        return num;
    }
}
public class MapDemo {
    public static void main(String[] args) {
        HashMap<Student,String> hm=new HashMap<Student,String>();
        hm.put(new Student("zhang", 18), "zunan");
        hm.put(new Student("zhang", 18), "hunan");
        hm.put(new Student("wang", 19), "wuhan");
        hm.put(new Student("li", 20), "beijing");
        //第一種取出方式 keySet
        Set<Student> keySet = hm.keySet();
        Iterator<Student> it=keySet.iterator();
        while(it.hasNext()){
            Student st = it.next();
            String addr = hm.get(st);
            System.out.println(st+" "+addr);
        }
        //第二種取出方式 entrySet
        Set<Map.Entry<Student,String>> entrySet = hm.entrySet();
        Iterator<Map.Entry<Student,String>> ite = entrySet.iterator();
        while(ite.hasNext()){
            Map.Entry<Student,String> me = ite.next();
            Student student = me.getKey();
            String addr = me.getValue();
            System.out.println(student+" "+addr);
        }
    }
}