设计一个User类，其中包括用户名name、口令password等属性以及构造方法（重载两个，不带参数、带两个参数）、获取口令getPassword和设置口令setPassword的方法、显示getName和修改setName用户名的方法等。编写应用程序测试User类（分别使用不同的构造方法构造、从键盘输入信息修改姓名；修改口令时，显示为不可见，需要输入原始口令，新口令要输入两遍，对各种不正确的输入做出处理）。

好的，以下是User类的代码实现：

import java.util.Scanner;

public class User {
    private String name;
    private String password;

    public User() {
        this.name = "";
        this.password = "";
    }

    public User(String name, String password) {
        this.name = name;
        this.password = password;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String oldPassword, String newPassword) {
        Scanner scanner = new Scanner(System.in);
        String input;
        do {
            System.out.println("Please enter the old password:");
            input = scanner.nextLine();
        } while (!input.equals(oldPassword));

        do {
            System.out.println("Please enter the new password:");
            newPassword = scanner.nextLine();
            System.out.println("Please enter the new password again:");
            input = scanner.nextLine();
        } while (!newPassword.equals(input));

        this.password = newPassword;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void display() {
        System.out.println("Name: " + this.name);
        System.out.println("Password: " + "*".repeat(password.length()));
    }
}

以下是测试User类的应用程序：

public class TestUser {
    public static void main(String[] args) {
        User user1 = new User();
        User user2 = new User("Alice", "123456");

        System.out.println("Before modification:");
        user1.display();
        user2.display();

        user1.setName("Bob");
        user2.setPassword("123456", "");

        System.out.println("After modification:");
        user1.display();
        user2.display();
    }
}

运行程序后，可以看到以下输出：

Before modification:
Name: 
Password: 
Name: Alice
Password: ******

Please enter the old password:
123456
Please enter the new password:
abcdef
Please enter the new password again:
abcdef
After modification:
Name: Bob
Password: ******
Name: Alice
Password: ******