初学java，自己用java写了一个简单的注册登录程序，没报错但有问题，希望能帮忙指点。

Question

import java.util.Scanner;
class Yanzheng{
private String n;
private String p;
public void setNa(String na){
this.n = na;
}
public void setPa(String pa){
this.p = pa;
}
public String getNa(){
return n;
}
public String getPa(){
return p;
}
public boolean fun1(String name,String password){
if(name.equals(getNa()) && password.equals(getPa())){
return true;
}
else{
return false;
}
}
}

class Caozuo{
private String name;
private String password;
public String str;
public void setName(String name){
this.name = name;
}
public void setPassword(String password){
this.password = password;
}
public String getName(){
return name;
}
public String getPassword(){
return password;
}
Yanzheng yz = new Yanzheng();
public String fun2(){
if(yz.fun1(getName(),getPassword())){
str = "欢迎" + name + " 帅哥光临";
}else{
str = "用户名或密码输入错误";
}
return str;
}
public void fun3(){
Scanner in = new Scanner(System.in);
String na = in.next();
String pa = in.next();
Yanzheng yz = new Yanzheng();
yz.setNa(na);
yz.setPa(pa);
}
}

public class ZhuceXitong{
public static void main(String args[]){
System.out.println("开始注册，请输入注册名和密码！");
Scanner in = new Scanner(System.in);
Caozuo cz = new Caozuo();
cz.fun3();
System.out.println("注册成功，请登录!");
System.out.println("请输入用户名和密码!");
String name = in.next();
String password = in.next();
cz.setName(name);
cz.setPassword(password);
System.out.println(cz.fun2());
}
}

Answer 1

你错的地方是在fun3方法内，不应该new一个Yanzheng类实例，方法内部new的且未做返回值进行返回的实例是局部的，把这行代码去掉就OK，
另外不太明白为什么你这么写，你操作类和验证类为什么分开呢？验证不一样是一种操作？然后你的用户信息也没做存储啊。下面我做了个实例，
希望能对你有用。

 package com.mdjin;

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

    class User{
        private String name;
        private String passWord;
        public String getPassWord() {
            return passWord;
        }
        public void setPassWord(String passWord) {
            this.passWord = passWord;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
    }

    class Caozuo {

        /**
         * 用户信息应该持久化的，此处用MAP对其进行存储.
         */
        Map<String,User> users = new HashMap<String,User>();

        public boolean zhuceyonghu(String _name,String _passWord){
            System.out.println(_name+_passWord);
            if(users.containsKey(_name)){
                System.out.println("用户名已被使用，请重新注册.");
                return false;
            }
            User user = new User();
            user.setName(_name);
            user.setPassWord(_passWord);
            users.put(_name, user);
            return true;
        }

        public boolean yanzhengyonghu(String _name,String _passWord){
            System.out.println(_name+_passWord);
            if(users.containsKey(_name)){
                User user = users.get(_name);
                if(user.getPassWord()!=null)
                    return _passWord.equals(user.getPassWord());
            }
            return false;
        }
    }

    public class ZhuceXitong2 {
        public static void main(String args[]) {
            System.out.println("开始注册，请输入注册名和密码！");
            Caozuo cz = new Caozuo();
            boolean flag = true;
            Scanner in = new Scanner(System.in);
            while(flag){
                String name = in.next();
                if(name.equals("quit")){
                    System.out.println("系统退出.");
                    return;
                }
                String password = in.next();
                flag = !cz.zhuceyonghu(name, password);
                if(flag){
                    System.out.println("注册失败，请重新输入用户名和密码，或者输入quit退出!");
                }
            }
            System.out.println("注册成功，请输入用户名和密码进行登录!");
            boolean flag2 = true;
            while(flag2){
                String name = in.next();
                if(name.equals("quit")){
                    System.out.println("系统退出.");
                    return;
                }
                String password = in.next();
                flag2 = !cz.yanzhengyonghu(name, password);
                if(flag2){
                    System.out.println("登录失败，请重新输入用户名和密码，或者输入quit退出!");
                }else{
                    System.out.println("欢迎："+name+"归来.");
                }
            }
        }
}