Java扫描器验证- Char，int，double，String

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整数，但如果他们输入其他内容，那么我希望为每种类型提供自定义消息。例如，

• char："您无法输入字母，请使用1-10中的数字"
• 双精度："您不能输入小数的数字，请使用1-10的整数"
• string：“请输入1-10的数字”

目前我正在使用这个代码，如果它不是整数，它只允许我显示一条消息

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

Answer 1

按照下面的方法去做，它会解决你的问题，

    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。下面的链接对它们进行了概述:

http://docs.oracle.com/javase/6/docs/api/java/util/Scanner.html#hasNext（java.lang.String）

Answer 2

希望这能帮到你。

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);