java - 如何编写特定的随机数方案？

Question

我正在学习Java。我只想编写一个方法来生成特定集合中的随机数，例如银行信用卡“xxxx - xxxx - xxxx - xxxx ”。每个 block 的长度必须恰好为 4 位数字。有人有解决办法吗？

public class Main {

public static User accountHolders[] = new User[100]; 公共(public)静态 int 索引 = 0;

public static void main(String[] args) {

    Scanner input = new Scanner(System.in);

    while (true) {

        System.out.println("\t-----\tWelcome to The Bank portal\t-----");
        System.out.println("\nPlease enter the number of your required action");
        System.out.println("\n1) Make a Deposit");
        System.out.println("2) Get balance");
        System.out.println("3) Register new account");
        System.out.println("0) Quit the portal");

        int command = input.nextInt();
        switch (command) {
            case 1:
                InputController.deposit();
                break;
            case 2:
                InputController.balance();
                break;
            case 3:
                User user = InputController.register();
                accountHolders[index] = user;
                index++;
                break;

                default:
                System.out.println("Wrong input! please enter a number between 1 - 4!!!");
                break;

        }
    }
}

}

public class Account {
private int uniID;
private int password;
private int balance;
private String cardNum;

public int getUniID() {
    return uniID;
}

public int getPassword() {
    return password;
}

public int getBalance() {
    return balance;
}
public void makeDeposit(int amount) {
    this.balance = this.balance + amount;
}

public Account(int password, int balance) {
    this.password = password;
    this.balance = balance;

    Random rand = new Random();
    this.uniID = rand.nextInt(100);



}

}

public class User {
private String name;
private Account account;

public String getName() {
    return name;
}


public Account getAccount() {
    return account;
}



public User(String name, Account account) {
    this.name = name;
    this.account = account;

}

}

public class InputController {

static Scanner input = new Scanner(System.in);

public static User register() {
    System.out.print("Enter your name: ");
    String name = input.next();
    System.out.print("Enter your password: ");
    int password = input.nextInt();
    System.out.print("Please enter the amount of your initial deposit: ");
    int balance = input.nextInt();

    Account account = new Account(password, balance);

    User user = new User(name, account);

    System.out.print("Your account number is: " + account.getUniID());


    return user;


}

public static void balance() {

    int index = findAccount();

    if (index != -1) {
        System.out.print("Enter your password: ");
        int password = input.nextInt();
        if (Main.accountHolders[index].getAccount().getPassword() == password) {
            System.out.println("Your balance is: " +
                    Main.accountHolders[index].getAccount().getBalance());
        } else {
            System.out.println("Wrong password");
        }

    }



}

public static void deposit() {


        int index = findAccount();
        if (index != -1) {
            System.out.print("Enter the required amount: ");
            int money = input.nextInt();
            Main.accountHolders[index].getAccount().makeDeposit(money);
            System.out.println("Deposit successful");
        }
    }


    private static int findAccount() {

        System.out.print("Please Enter your account number: ");
        int accountNum = input.nextInt();

        for (int i = 0; i < Main.index; i++) {

            User user = Main.accountHolders[i];
            int id = user.getAccount().getUniID();

            if (id == accountNum) {
                return i;

            } else if (id != accountNum){
                System.out.println("Account number not found");

            }

        }

        return -1;
    }
}

抱歉，有点长，但现在这就是全部内容了。我想在信用卡号用户每次注册新帐户时引入一个新变量。

Answer 1

你可以尝试下面的代码吗？如果你只想一次，只需删除 for 循环即可。

public class RandomSetGenerator {
public static void main(String[] args) {
    Random generator = new Random();
    for (int i = 0; i < 10; i++) {
        String string = Integer.toString(generator.nextInt(9000) + 1000) + "-" + Integer.toString(generator.nextInt(9000) + 1000) + "-" + Integer.toString(generator.nextInt(9000) + 1000) + "-" + Integer.toString(generator.nextInt(9000) + 1000);
        System.out.println("Specific set of random  number generated :" + string);
    }
}}