java編程中，如果輸入驗證失敗，如何讓用戶重試3次才拋出異常並終止？

Question

java編程中，如果輸入驗證失敗，如何讓用戶重試3次才拋出異常並終止？ •

Sample Run
Enter taxable income ... 80
The taxable income must be at least $1200.0
Enter taxable income ... 890
The taxable income must be at least $1200.0
Enter taxable income ... 1090
The taxable income must be at least $1200.0
Exception in thread "main" java.lang.RuntimeException: Sorry
you're having trouble

Answer 1

使用循環，其中

• 讀取並驗證用戶的輸入。
• 如果驗證工作正常退出循環
• 如果驗證失敗
  • 增加tries counter
  • 如果tries counter將大於預定義的最大拋出運行時異常與您的消息。

Answer 2

謝謝大家。 @pshemo 你是對的，這是一項家庭作業，所以如果第三次嘗試后輸入驗證失敗，我必須強制使用“ToolBox.crash”方法來終止程序。 我按照你的建議解決了這個問題。 我在循環內初始化了一個循環計數器。 這是計算個人所得稅的程序的完整代碼。

import java.util.Scanner;
import java.io.PrintStream;
import type.lib.ToolBox;

public class L5B
{

    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        PrintStream output = System.out;

        final double MIN_AMOUNT = 1200.0;
        final double BASIC_AMOUNT = 43561.0;
        final double LEVEL_ONE = 43561.0 + 43562.0;
        final double LEVEL_TWO = LEVEL_ONE + 47931.0;
        final double TWENTY_ONE = 21/100.0;
        final double THIRTY_THREE = 33/100.0;
        final double THIRTY_EIGHT = 38/100.0;
        final double HUNDRED = 100.0;
        final double FORTY_TWO = 42/100.0;
        final int THREE = 3;
        final int TWO = 2;


        output.print("Enter taxable income ... ");
        double income;
        int i = 0;
        for(income = input.nextDouble(); income < MIN_AMOUNT; )
        {

            output.println("The taxable income must be at least " + MIN_AMOUNT);
            output.print("Enter taxable income ... ");
            income = input.nextDouble();
            i++;

                if(i >= TWO)
                {
                        ToolBox.crash(true,"Sorry you're having trouble.");
                }           
        }


        if (income <= BASIC_AMOUNT)
        {
            double totalTax = income * TWENTY_ONE;
            double averageRate = TWENTY_ONE * HUNDRED;
            double marginalRate = averageRate;
            output.printf("Tax = %,.2f", totalTax);
            output.printf("\nAverage Rate = %.1f%%", averageRate);
            output.printf("\nMarginal Rate = %.1f%%", marginalRate);

        }
        else if (income > BASIC_AMOUNT && income <= LEVEL_ONE)
        {
            double totalTax = BASIC_AMOUNT * TWENTY_ONE + ((income - BASIC_AMOUNT)*THIRTY_THREE);
            double averageRate = HUNDRED*totalTax/income;
            double marginalRate = THIRTY_THREE*HUNDRED;
            output.printf("Tax = %,.2f", totalTax);
            output.printf("\nAverage Rate = %.1f%%", averageRate);
            output.printf("\nMarginal Rate = %.1f%%", marginalRate);
        }
        else if (income > LEVEL_ONE && income <= LEVEL_TWO)
        {
            double totalTax = BASIC_AMOUNT * TWENTY_ONE + (LEVEL_ONE - BASIC_AMOUNT) * THIRTY_THREE + ((income - LEVEL_ONE) * THIRTY_EIGHT);
            double averageRate = totalTax*HUNDRED/income;
            double marginalRate = THIRTY_EIGHT*HUNDRED;
            output.printf("Tax = %,.2f", totalTax);
            output.printf("\nAverage Rate = %.1f%%", averageRate);
            output.printf("\nMarginal Rate = %.1f%%", marginalRate);
        }
        else if (income > LEVEL_TWO)
        {
            double totalTax = BASIC_AMOUNT * TWENTY_ONE + ((LEVEL_ONE - BASIC_AMOUNT) * THIRTY_THREE) + ((LEVEL_TWO - LEVEL_ONE) * THIRTY_EIGHT) + ((income - LEVEL_TWO) * FORTY_TWO);
            double averageRate = totalTax*HUNDRED/income;
            double marginalRate = FORTY_TWO * HUNDRED;
            output.printf("Tax = %,.2f", totalTax);
            output.printf("\nAverage Rate = %.1f%%", averageRate);
            output.printf("\nMarginal Rate = %.1f%%", marginalRate);
        }



    }   
}