[JAVA]通过HashMap实现的增删改查小例子

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
 
class Student
{
    String name;
    String details;
 
    int age;
 
    public Student(String name, String details, int age)
    {
        this.name = name;
        this.details = details;
        this.age = age;
    }
 
    public String toString()
    {
        return "name: " + name + ", details: " + details + ", age: " + age;
    }
}
 
public class A {
    private static Map map = new HashMap();
 
    public static void Register()
    {
        System.out.println("Register:");
        map.put("1", new Student("Jack", "shuaiguo", 11));
        map.put("2", new Student("Rose", "meilv", 12));
        map.put("3", new Student("Lucy", "na", 13));
        System.out.println("");
    }
    public static void Update(String id, Student student)
    {
        System.out.println("Update:");
        map.put(id, student);
        System.out.println(student.age);
        System.out.println("");
    }
 
    public static boolean Login(String id, String name)
    {
        System.out.println("Login id:" + id + ", name: " + name);
        Student value = (Student) map.get(id);
        String result = value.name.equals(name) ? "successfully" : "failed";
        System.out.println("Login " + result);
        System.out.println("");
        return value.name.equals(name);
    }
 
    public static void QueryAll()
    {
        System.out.println("QueryAll:");
        Set set = map.keySet();
        Iterator iterator = set.iterator();
        while (iterator.hasNext())
        {
            String key = (String) iterator.next();
            Student value = (Student) map.get(key);
            System.out.println("id: " + key +": "+  value.toString());
        }
        System.out.println("");
    }
 
    public static void Delete(String id)
    {
        System.out.println("Delete id: " + id);
        map.remove(id);
        System.out.println("");
    }
 
    public static void main(String[] args)
    {
        //ADD
        Register();
 
        //QUERY
        QueryAll();
 
        //QUERY
        Login("2", "Rose"); //另一个测试手段：Login("2", "Rose");
 
        //MODIFY
        Update("3", new Student("Lucy_new", "aa", 16));
        QueryAll();
 
        //DELETE
        Delete("1");
        QueryAll();
    }
}