java - Java中使用try-catch处理输入异常

Question

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已关闭 3 年前。

我已经为此工作了几个小时，但我无法理解如何在这两个 do while 循环中实现 try-catch 来捕获用户输入的非 int 值。我知道有这方面的帖子，但我似乎看不到。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");

    }
}

Answer 1

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

double wallHeight = 0;
double wallWidth = 0;

然后您需要将 scnr.nextDouble(); 放入 try block 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catch block 中的scnr.next();。您需要执行此操作才能使用无效 token 。否则它永远不会从缓冲区中删除，并且 scnr.nextDouble(); 将继续尝试读取它并立即抛出异常。