如何通过在 Try-Catch While 循环中输入特定字母来退出程序？答案

【问题标题】：How to quit program by entering specific letter while inside a Try-Catch While Loop?如何通过在 Try-Catch While 循环中输入特定字母来退出程序？
【发布时间】：2019-04-18 23:12:25
【问题描述】：

基本上我想在用户输入字母“q”而不是整数时退出程序。

尝试了几个小时，尝试通过添加解决它

if(quit.equalsIgnoreCase("q")){
System.exit(0)
}

在 try 语句中。尝试从 try 语句中删除 Scanner 并将其添加到 while 循环之前，然后像这样创建一个新变量：

String quit = "";
while (quit != "q"){
      //code
}

然后在代码中再次添加一种退出方式，但这不起作用。

 while (true) {

                try {
                    int randomNumberOne = ThreadLocalRandom.current().nextInt(10, 21); //generates a number between 10 and 20
                    int randomNumberTwo = ThreadLocalRandom.current().nextInt(10, 21); //generates a number between 10 and 20
                    System.out.println("Type and enter \"q\" to quit at any time \n \n");

                    System.out.println(randomNumberOne + " % " + randomNumberTwo + " = ?"); //prints the question

                    Scanner userInput = new Scanner(System.in);
                    int remainderInput = userInput.nextInt();

                    if (remainderInput == randomNumberOne % randomNumberTwo) { //if they get the question right
                        userScore += 20; //adds 20 points
                        performance += 1; //adds 1 to the correct question counter
                        performancetotal += 1; //adds 1 to the total question counter
                        System.out.println("Correct answer, Current Score: " + userScore + ", performance: " + performance + "/" + performancetotal + "\n");
                        continue;
                    }

                    else { //if they get the question wrong
                        userScore += 0; //adds no points
                        performance += 0; //adds nothing to correct question counter
                        performancetotal += 1;
                        System.out.println("Incorrect answer, Current Score: " + userScore + ", performance: " + performance + "/" + performancetotal + "\n");
                        continue;
                    }

                 }

                catch (InputMismatchException e) {
                    System.out.println("Invalid input\n");

                }

         }
    }

这是我当前的代码，除了顶部的一些变量不应该影响代码。

程序应该永远运行，直到用户输入“q”，然后它将停止运行。那里有 try/catch 语句，因此它们只能输入整数（当然“q”除外）。

任何帮助将不胜感激。

【问题讨论】：

程序永远运行，直到用户输入“q”，然后它就会停止运行。 这不是重点吗？有什么问题？
@shmosel 抱歉。意思是“程序应该永远运行”。只是试图解释它的作用。问题是我找不到让它退出atm的方法。显然我已经尝试过诸如 System.exit(0) 之类的东西，但它不起作用。
您当前的 sn-p 没有 break; 语句或 while 条件，那么您为什么希望它停止？
你想设置一个标志（布尔值是好的），当输入 q 并检查你的 while 循环与那个标志。

标签： java while-loop try-catch exit

【解决方案1】：

您可以尝试使用nextLine() 来获取字符串，而不是使用Scanner.nextInt() 方法。然后您可以检查该字符串是否等于“q”。如果不是，您可以使用Integer.parseInt(yourString) 将字符串解析为整数。但是，如果用户输入的不是数字或“q”，这可能会导致 NumberFormatException。

while (true) {

            try {
                int randomNumberOne = ThreadLocalRandom.current().nextInt(10, 21); //generates a number between 10 and 20
                int randomNumberTwo = ThreadLocalRandom.current().nextInt(10, 21); //generates a number between 10 and 20
                System.out.println("Type and enter \"q\" to quit at any time \n \n");

                System.out.println(randomNumberOne + " % " + randomNumberTwo + " = ?"); //prints the question

                Scanner userInput = new Scanner(System.in);
                String remainderInputStr = userInput.nextLine();
                if (remainderInputStr.equalsIgnoreCase("q")) {
                    System.exit(0);
                }
                int remainderInput = Integer.parseInt(remainderInputStr);
                if (remainderInput == randomNumberOne % randomNumberTwo) { //if they get the question right
                    userScore += 20; //adds 20 points
                    performance += 1; //adds 1 to the correct question counter
                    performancetotal += 1; //adds 1 to the total question counter
                    System.out.println("Correct answer, Current Score: " + userScore + ", performance: " + performance + "/" + performancetotal + "\n");
                    continue;
                } else { //if they get the question wrong
                    userScore += 0; //adds no points
                    performance += 0; //adds nothing to correct question counter
                    performancetotal += 1;
                    System.out.println("Incorrect answer, Current Score: " + userScore + ", performance: " + performance + "/" + performancetotal + "\n");
                    continue;
                }

            } catch (NumberFormatException e) {
                System.out.println("Invalid input\n");

            }

【讨论】：