Java封装1-9的编程练习中checkUser的问题

public class User{

    //定义属性用户名、密码

    private String name;

    private String password;

    public User(String name,String password){

    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;

}

}

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public class UserManager {

// 用户信息验证的方法

public String checkUser(User one, User two) {//如果吧String改成void运行效果一样，这地方可以写成void吗？

// 判断用户名是否为空，是否一致

if((two.getName()==null)&&(one.getName()==null)){

System.out.println("用户名为空");

}else if(one.getName().equals(two.getName())){

System.out.println("用户名正确");

}else{

System.out.println("用户名错误");

}

if((one.getPassword()==null)&&(two.getPassword()==null)){

System.out.println("密码为空");

}else if(one.getPassword().equals(two.getPassword())){

System.out.println("密码正确");

}else{

System.out.println("密码错误");

}

// 判断密码是否为空，是否一致

return "";

}

}

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public class Test {

// 测试方法

public static void main(String[] args) {

//实例化对象，调用相关方法实现运行效果

User one=new User("Lucy","123456");

User two=new User("Mike","123456");

UserManager mananger=new UserManager();

System.out.println(one.getName());

System.out.println(one.getPassword());

System.out.println(two.getName());

System.out.println(two.getPassword());

System.out.println("============");

mananger.checkUser(one,two);

}

}