JAVA HASHMAP 用法

import java.util.HashMap;
public class Student {
    String name;
    String sex;
    public Student(String n,String s) {
        name=n;
        sex=s;
    }
    public String toString(){
       return ("姓名:"+name+"\n"+"性别:"+sex+"\n"); 
    }
    public static void main(String [] args){
        HashMap hm=new HashMap();
        Student s1=new Student("张三","男");
        Student s2=new Student("李四","男");
        Student s3=new Student("小利","女");

        //存值是根据学生编号存的学生信息
        hm.put("001",s1);
        hm.put("002",s2);
        hm.put("003",s3);
        
        //查找学生编号是001的学生
        
        //因为hm.get("001")反回的是Object所以加上强转
        Student s=(Student)hm.get("001");
        System.out.println(s.toString());
        
        //其余的类似
        
    }
}