Question

如何为输入的不同类型的数据显示不同的消息？我只希望用户能够输入一个整数，但如果他们输入其他内容，那么我想要为每种类型添加自定义消息。例如，

char：“你不能输入一封信，请使用1-10”
double：“您不能输入带小数的数字，请使用1-10”
字符串：“请输入1-10”

目前我正在使用此代码，只允许我显示一条消息（如果它不是整数

）

printMenuOption();
if (!sc.hasNextInt()){
    System.out.println("Please enter a number from 1 to 10");
    sc.nextLine();
}else{
    returnDataMenu(sc.nextInt());
}

Answer 1

我希望这会对你有所帮助。

Scanner myInput = new Scanner(system.in);

do {
    printMenuOption();
    if (!myInput.hasNextInt()){

        if(myInput.hasNextDouble()){

            System.out.println("You can not use a decimal number!");
            System.out.println("Please try again, choose a number from 1 to 10.");


        }else if(myInput.nextLine().length() <= 1){

            System.out.println("You can not use a character as an entry");
            System.out.println("Please try again, choose a number from 1 to 10.");


        }else if(myInput.nextLine().length() > 1){

            System.out.println("You can not enter a string");
            System.out.println("Please try again, choose a number from 1 to 10.");

        }
        else{

            System.out.println("Please enter a number from 1 to 10");
            userInput = myInput.nextLine();
        }



    }
    else{

        returnDataMenu(myInput.nextInt());
    }

} while (cont == true);

Answer 2

如下所示，它将解决您的问题，

    while (sc.hasNext()) {
                if (sc.hasNextInt()) {
                    returnDataMenu(sc.nextInt());
                } else if (sc.hasNextLong()) {
                    System.out.println("You can't enter a long number, please use a whole number from 1-10");
                } else if (sc.hasNextDouble()) {
                    System.out.println("You can't enter a number with a decimal, please use a whole number from 1-10");
                } else if (sc.hasNextBoolean()) {
                    System.out.println("You can't enter a boolean, please use a whole number from 1-10");
                } else if (sc.next() != null) {
                    System.out.println("You can't enter a string, please use a whole number from 1-10");
                } else if (sc.nextLine().length() <= 1) {
                    System.out.println("You can't enter a char, please use a whole number from 1-10");
                }
}

java.util.Scanner有许多hasNextXXX方法可用于验证输入。以下链接概述了所有这些内容：

http://docs.oracle.com/javase/6/docs/api/java/util/Scanner.html#hasNext%28java.lang.String%29

Java扫描程序验证 - Char，int，double，String

2 个答案: