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java - Java中使用try-catch处理输入异常

问题描述

我已经为此工作了几个小时，我只是无法理解如何在这两个 do while 循环中实现 try-catch 以捕获用户输入非整数。我知道有这方面的帖子，但我似乎无法得到它。我非常感谢任何建议。

public class Paint {
    public static void main(String[] args) {
        Scanner scnr = new Scanner(System.in);

        double wallHeight;
        double wallWidth;
        double wallArea = 0.0;
        double gallonsPaintNeeded = 0.0;
        final double squareFeetPerGallons = 350.0;

        // Implement a do-while loop to ensure input is valid
        // Handle exceptions(could use try-catch block)
        do {
            System.out.println("Enter wall height (feet): ");
            wallHeight = scnr.nextDouble();
        } while (!(wallHeight > 0));
        // Implement a do-while loop to ensure input is valid
        // Handle exceptions(could use try-catch block)
        do {
            System.out.println("Enter wall width (feet): ");
            wallWidth = scnr.nextDouble();
        } while (!(wallWidth > 0));

        // Calculate and output wall area
        wallArea = wallHeight * wallWidth;
        System.out.println("Wall area: " + wallArea + " square feet");

        // Calculate and output the amount of paint (in gallons) 
        // needed to paint the wall
        gallonsPaintNeeded = wallArea/squareFeetPerGallons;
        System.out.println("Paint needed: " + gallonsPaintNeeded + " gallons");

    }
}

标签： javatry-catchinputmismatchexception

解决方案

首先在类中将 wallHeight 和 wallWidth 初始化为一个临时值（我们将使用 0）：

double wallHeight = 0;
double wallWidth = 0;

然后你想放入scnr.nextDouble();块try中以捕获解析错误：

do {
        System.out.println("Enter wall height (feet): ");
        try{
            wallHeight = scnr.nextDouble();
        }catch(InputMismatchException e){
            scnr.next(); //You need to consume the invalid token to avoid an infinite loop
            System.out.println("Input must be a double!");
        }
    } while (!(wallHeight > 0));

注意块scnr.next();中的。catch您需要执行此操作才能使用无效令牌。否则它将永远不会从缓冲区中删除，并且scnr.nextDouble();会继续尝试读取它并立即抛出异常。

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