Java-Map应用实例

/*
* 每个学生都有对应的归属地。
* 学生Student,地址String.
* 学生属性：姓名，年龄。
* 注意：姓名和年龄相同的视为同一个学生。
* 保证学生的唯一性。
*
* 1.描述学生。
* 2.定义map容器。将学生作为键，地址作为值，存入。
* 3.获取map集合中的元素。
*/

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 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;
   }
   public int getAge() {
       return age;
   }

   public String toString() {
       return name+":"+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;
   }

}

public class MapTest {

   public static void main(String[] args) {
       // TODO Auto-generated method stub
       HashMap<Student,String> hm = new HashMap<Student,String>();

       hm.put(new Student("lisa",21),"beijing");
       hm.put(new Student("lisb",22),"shanghai");
       hm.put(new Student("lisc",23),"shenzhen");
       hm.put(new Student("lisd",24),"guangzhou");

       //第一种取出方式
       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+"----"+addr);
       }

       //第二种取出方式
       Set<Map.Entry<Student, String>> entrySet = hm.entrySet();

       Iterator<Map.Entry<Student, String>> it1 = entrySet.iterator();

       while(it1.hasNext()) {
           Map.Entry<Student, String> me = it1.next();
           Student stu = me.getKey();
           String addr = me.getValue();
           System.out.println(stu+"===="+addr);
       }

}

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