Question

我试图用一种方法不捕获任何输入（输入键），并且将除y / n外的所有内容都无效输入。我尝试了两种不同的方式（粘贴），但是我无法同时进行“输入密钥”和“错误键入y / n”的工作。谢谢您的帮助。

第一次尝试：

public static String askToContinue(Scanner sc) {

String choice = "";
boolean isValid = false;

while (!isValid){System.out.print("Continue? (y/n): ");
    if (sc.hasNext()){
        choice = sc.next();
        isValid = true;
    } else {System.out.println("Error! "
                + "This entry is required. Try again");    
    }

    if (isValid && !choice.equals("y") || !choice.equals("n")) {
        System.out.println("Error! Entry must be 'y' or 'n'. Try again");
        isValid = false;
    }
   }
    //sc.nextLine();  // discard any other data entered on the line
    System.out.println();
    return choice;
   }        



   2nd attempt

    public static String askToContinue(Scanner sc) {
    System.out.print("Continue? (y/n): ");
    String choice;



    while (true) {choice = sc.next();

    //?????????????????????????????????????????????????????
        if (choice.length() == 0){ System.out.println("Error! "
                + "This entry is required. Try again");
            continue;
        }


        if (!(choice.equals("y") || choice.equals("n"))) {
            System.out.println("Error! Entry must be 'y' or 'n'. Try                   again");
            continue;
        }

        break;    
    }

    sc.nextLine();  // discard any other data entered on the line
    System.out.println();
    return choice;
    }

Answer 1

您的if陈述式在第一种情况下是错误的。您正在检查选择=SUBSTITUTE(LEFT(A2,FIND(" ",A2)-1),".","/")+SUBSTITUTE(MID(A2,FIND(" ",A2)+1,99),".",":") 或 is not equal to 'y'是否始终为真。

更改

not equal to 'n'

收件人

if (isValid && !choice.equals("y") || !choice.equals("n"))

Answer 2

我尝试了您的代码的第一次尝试。我用注释行进行了说明，该注释行包含在以下代码中；

public static String askToContinue(Scanner sc) {
    String choice = "";
    boolean isValid = false;
    while (!isValid) {
        System.out.print("Continue? (y/n): ");
        choice = sc.nextLine(); //to reads all line , because this cannot read with empty enter input
        isValid = true;
        if (choice.isEmpty()) {  //this isEmpty for empty enter
            System.out.println("Error! "
                    + "This entry is required. Try again");
        }
        System.out.println(choice);
        //this logic if not y or n , it will return error
        if (!choice.equals("y") && !choice.equals("n")) {
            System.out.println("Error! Entry must be 'y' or 'n'. Try again");
            isValid = false;
        }
    }
    //sc.nextLine();  // discard any other data entered on the line
    System.out.println();
    return choice;
}

是/否输入验证，不包括输入Enter键

2 个答案: