集合(Map练习)

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每一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

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;    }         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 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 String getName()    {        return name;    }    public int getAge()    {        return age;    }    public String toString()    {        return name+":"+age;    }} class MapTest{    public static void main(String[] args)    {        HashMap<Student,String> hm = new HashMap<Student,String>();                 hm.put(new Student("lisi1",21),"beijing");        hm.put(new Student("lisi2",22),"shanghai");        hm.put(new Student("lisi3",23),"nanjing");        hm.put(new Student("lisi4",24),"wuhan");                 //第一种取出方式 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+".."+addr);        }                 //第二种取出方式 entrySet        Set<Map.Entry<Student,String>> entrySet = hm.entrySet();                 Iterator<Map.Entry<Student,String>> iter = entrySet.iterator();                 while(iter.hasNext())        {            Map.Entry<Student,String> me = iter.next();            Student stu = me.getKey();            String addr = me.getValue();            System.out.println(stu+"........."+addr);        }    }}

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