使用序列化完成注册及登录

import java.io.Serializable;

/**
 * @author Administrator
 *    用户信息封装
 */
public class User implements Serializable{
    private String name;
    private String password;
    public User() {}
    public User(String name, String password) {
        super();
        this.name = name;
        this.password = password;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

import java.io.File;
import java.io.Serializable;
import java.util.HashMap;

/**
 * @author Administrator
 *    创建Map集合，存放用户信息
 */
public class UserInit implements Serializable{
    static HashMap<String,User> users = new HashMap<>(); //创建存放用户的集合
    static {
        ObjectOutInputStreamDome.oboi("Verde","123456");
    }
}

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;

/**
 * @author Administrator
 *    序列化输出流
 */
public class ObjectOutInputStreamDome {
    public static void oboi(String name,String password) {
        FileOutputStream fo = null;
        ObjectOutputStream oos = null;
        
        try {
            fo = new FileOutputStream("G:/垃圾/User.txt");
            oos = new ObjectOutputStream(fo);
            User user = new User(name,password);
            UserInit.users.put(name, user);
            oos.writeObject(UserInit.users);
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            try {
                if(oos!=null) {
                    oos.flush();
                    oos.close();
                }
                if(fo!=null) {
                    fo.close();
                }
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

/**
 * @author Administrator
 *    序列化输入流
 */
public class ObjextInputStreamDome {
    public static HashMap<String,User> obin() {
        FileInputStream fi = null;
        ObjectInputStream ois = null;
        
        try {
            fi = new FileInputStream("G:/垃圾/User.txt");
            ois = new ObjectInputStream(fi);
            HashMap<String, User> users = (HashMap<String, User>)ois.readObject();
            return users;
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            try {
                ois.close();
                fi.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return null;
    }
}

/**
 * @author Administrator
 *    登录操作
 */
public class UserLogin {
    //登录
    public static void Login() {
        boolean flag = false;
        do {
            System.out.println("请输入登录账号：");
            String name = TestDome.input.next();
            System.out.println("请输入密码：");
            String password = TestDome.input.next();
            flag = isexist(name,password);
            if(flag) {
                return;
            }else {
                System.out.println("用户名不存在或者密码错误，请重新输入！");
            }
        }while(!flag);
        
        
    }
    
    //判断是否正确
    public static boolean isexist(String name,String password) {
        HashMap<String, User> users = ObjextInputStreamDome.obin();
        Set<String> keys = users.keySet();
        for(String key:keys) {
            User user = users.get(key);
            if(user.getName().equals(name)&&user.getPassword().equals(password)) {
                System.out.println("登录成功！");
                return true;
            }
        }
        return false;
    }
}

import java.util.HashMap;
import java.util.Set;

/**
 * @author Administrator
 *    注册操作
 */
public class UserLogon {
    //注册
    public static void Logon() {
        boolean flag = true;
        do {
            System.out.println("请输入账号名：");
            String name = TestDome.input.next();
            System.out.println("请输入登录密码：");
            String password = TestDome.input.next();
            ObjectOutInputStreamDome.oboi(name, password);
            flag = isexist(name,password);
            if(flag) {
                return;
            }
        }while(!flag);
        
    }
    
    // 判断存在
    public static boolean isexist(String name,String password) {
        HashMap<String, User> users = ObjextInputStreamDome.obin();
        Set<String> keys = users.keySet();
        for (String key : keys) {
            User user = users.get(key);
            if (!user.getName().equals(name) ) {
                System.out.println("注册成功！");
                ObjectOutInputStreamDome.oboi(name, password);
                return true;
            }
        }
        System.out.println("用户名已存在，请重新输入！");
        return false;
    }
}

/**
 * @author Administrator
 *    测试类
 */
public class TestDome {
    static Scanner input = new Scanner(System.in);
    public static void main(String[] args) {
        System.out.println("1、登录	2、注册");
        String choose = input.next();
        switch (choose) {
        case "1":
            UserLogin.Login();
            break;
        case "2":
            UserLogon.Logon();
            break;
        default:
            break;
        }
    }
}