扫描仪异常重试 [英] Scanner Exception Retry

问题描述

如何在异常发生时重试扫描器？

考虑此应用程序在CLI模式下运行。

How to make scanner retry when exception occur?
Consider this app running on CLI mode.

示例：

System.out.print("Define width: ");
    try {
        width = scanner.nextDouble();
    } catch (Exception e) {
        System.err.println("That's not a number!");
        //width = scanner.nextDouble(); // Wrong code, this bring error.
    }

如果用户未输入 double 输入，然后引发错误。但是我想要错误消息出现后。应该要求用户再次输入 width 。

If the user not inputting double type input, then the error thrown. But i want after the error message appears. It's should be asking the user input the width again.

该怎么做？

推荐答案

如果我正确理解了您的要求，则希望该程序要求用户在输入失败后重新输入正确的输入。在这种情况下，您可以执行以下操作：

If I understood you correctly, you want the program to ask the user to re-enter a right input after it fails. In that case you can do something like:

boolean inputOk = false;
while (!inputOk) {
    System.out.print("Define width: ");
    try {
        width = scanner.nextDouble();
        inputOk = true;
    } catch (InputMismatchException e) {
        System.err.println("That's not a number!");
        scanner.nextLine();   // This discards input up to the 
                              // end of line
        // Alternative for Java 1.6 and later
        // scanner.reset();   
    }
}

注意：您只能 捕获并重试 InputMismatchException 。 nextXxx 方法抛出其他异常，如果您尝试重试这些异常，则应用程序将陷入无限循环。

Note: you should only catch and retry for a InputMismatchException. The nextXxx methods throw other exceptions, and if you attempt to retry those, your application will go into an infinite loop.

这篇关于扫描仪异常重试的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！