检查两个整数输入是否在范围内 - java

Question

我想检查两个整数输入是否在范围内且合法。以下代码是我想出的。

问题是当我检查第一个输入是否在范围内时，它不会弹出错误（不正确时），直到我输入第二个输入是否正确。当错误出现时，它只会打印错误以及等待用户输入的空行（没有明显原因）；我在其中输入任何内容并点击“输入”，然后程序再次运行（继续循环），要求用户再次输入值，直到它正确为止。

输入字符时不会出现此问题。输入不匹配的错误非常有效。它打印错误，然后再次运行程序，要求用户再次输入值，直到它是合法的。

如何让它检查第一个输入以查看它是否在范围内，如果在用户点击输入后立即输出错误，然后检查第二个输入并执行相同操作？

这有意义吗？

public String totalTime(){

    flag = 1;

    do{
        try{
            System.out.print("Enter a starting destination: ");
            int choice1 = user_input.nextInt();

            System.out.print("Enter a final desination: ");
            int choice2 = user_input.nextInt();

            if( (choice1 >= 1 && choice1 <= 5) && (choice2 >= 1 && choice2 <= 5) ){
                switch(choice1){

                    case 1: if (choice2 == 2){hour = 0; minutes = 10;} else if (choice2 == 3){hour = 0; minutes = 30;} else if (choice2 == 4) {hour = 1; minutes = 10;} else if (choice2 == 5) {hour = 1; minutes = 5;} break;
                    case 2: if (choice2 == 1){hour = 0; minutes = 10;} else if (choice2 == 3){hour = 0; minutes = 25;} else if (choice2 == 4) {hour = 1; minutes = 0;} else if (choice2 == 5) {hour = 0; minutes = 15;} break;
                    case 3: if (choice2 == 1){hour = 0; minutes = 48;} else if (choice2 == 2){hour = 0; minutes = 23;} else if (choice2 == 4) {hour = 0; minutes = 45;} else if (choice2 == 5) {hour = 0; minutes = 12;}break;
                    case 4: if (choice2 == 1){hour = 1; minutes = 5;} else if (choice2 == 2){hour = 1; minutes = 0;} else if (choice2 == 3) {hour = 0; minutes = 45;} else if (choice2 == 5) {hour = 0; minutes = 40;}break;
                    case 5: if (choice2 == 1){hour = 0; minutes = 30;} else if (choice2 == 2){hour = 0; minutes = 15;} else if (choice2 == 3) {hour = 0; minutes = 10;} else if (choice2 == 4) {hour = 0; minutes = 40;}break;
                    default: System.out.println("There is no such route");

                }
                flag = 2;
            }
            else if (choice1 < 1 || choice1 > 5 || choice2 < 1 || choice2 > 5){
                throw new NumberFormatException("Integer is out of range.");
            }
        }
        catch(NumberFormatException e){

            System.out.println("The number is not between 1 and 5. Try again.");
            System.out.println();
            user_input.next(); //removes leftover stuff from input buffer


        }
        catch(InputMismatchException e){

            System.out.println("This is not an integer. Try again.");
            System.out.println();
            user_input.next(); //removes leftover stuff from input buffer

        }
    }while (flag == 1);
    return ("The total time is " + hour + " hours and " + minutes + " minutes");
}

Answer 1

要验证并重新请求用户输入，您需要在 while 循环中请求输入，并且在输入有效之前不要离开循环。

所以在要求第一个输入后，您可以立即执行类似的操作

System.out.println("Enter a starting destination: ");
        int choice1 = user_input.nextInt();

while(choice1 < 1 || choice1 > 5) {
  System.out.println("Invalid Input");
  if(user_input.hasNextInt())
      choice1 = user_input.nextInt();
  else
      user_input.next();
}

System.out.println("Enter a final desination: ");
        int choice2 = user_input.nextInt();

while(choice2 < 1 || choice2 > 5 || choice2 == choice1) {
  System.out.println("Invalid Input");
  if(user_input.hasNextInt())
      choice2 = user_input.nextInt();
  else
      user_input.next();
}

这种方式还可以避免抛出仅用于控制程序流程的不必要的错误（可能非常难以阅读）