Question

我正在编写一个简单的模拟作为我研究的一部分（是的，我只是Java的初学者）。在其中我通过扫描仪从用户那里获取输入，我想检查输入是否有效格式（仅限数字）和有效范围。我遇到了困难 - 输入值不是来自“while”循环。你能给我一个提示吗？我会很感激的！

以下是您可能感兴趣的代码的一部分：

// check for invalid input
String input;
boolean valid = false;
while (!valid){
    try{
        input = sc.next();
        user = Integer.parseInt(input);
        valid = true;
    }catch (NumberFormatException ex) {
        System.out.println(ex);
        System.out.println("Number but not a character or a symbol!");
    }
    System.out.println("Try once more!");
}
// interaction with user;
while (user !=3){
    if (user ==1){
        System.out.println("What angle I should set?");
        userChange = sc.nextDouble();
        shot.userAngle(userChange);
        shot.show();
    }
    else if (user ==2){
        System.out.println("What speed I should set?");
        userChange = sc.nextDouble();
        shot.userSpeed(userChange);
        shot.show();
    }
    else {
        System.out.println("Wrong number!");
    }
    System.out.println("What you want to change?");
    user = sc.nextInt();
}

它表示可能未设置变量“user”。

Answer 1

SOLED。这里的工作代码

    int user; 
    double userChange;
    boolean stop = false;

    // check for invalid input if not integer and if out of range
    // interaction with user
    while (!stop){
        try {
            System.out.println("What you want to change?");
            user = sc.nextInt();
            if (user ==3){
                    stop = true;
                }

            while (user !=3){
                if (user ==1){
                    System.out.println("What angle I should set?");
                    userChange = sc.nextDouble();
                    shot.userAngle(userChange);
                    shot.show();
                }
                else if (user ==2){
                    System.out.println("What speed I should set?");
                    userChange = sc.nextDouble();
                    shot.userSpeed(userChange);
                    shot.show();
                }

                else {
                    System.out.println("Wrong number!");
                }
                System.out.println("What you want to change?");
                user = sc.nextInt();
                if (user ==3){
                    stop = true;
                }
            }
        }
        catch (InputMismatchException e){
            System.out.println(e);
            System.out.println("Wrong input! Number but not a symbol or a character!");
            sc.next();

        }
    }

检查有效输入并进一步使用输入

1 个答案: