Java源码-第一个异常处理小程序：整数除法

Java how to program（中文名：Java大学教程）第10版第11章：深入理解异常（Exception Handling: A Deeper Look）中给出了一个整数除法的示例，用户输入除数和被除数时，任何一个出错，就必须重新来过。考虑到这样做不太人性化，决定改写一下。

代码如下：

package exercise;

//Fig. 11.3: DivideByZeroWithExceptionHandling.java
//Handling ArithmeticExceptions and InputMismatchExceptions.
import java.util.InputMismatchException;
import java.util.Scanner;

public class FirstExceptionHandler
{
//demonstrates throwing an exception when a divide-by-zero occurs
public static int quotient(int numerator, int denominator)
 throws ArithmeticException
{
 return numerator / denominator; // possible division by zero
} 

public static void main(String[] args)
{
 Scanner scanner = new Scanner(System.in); 
 boolean continueLoop = true; // determines if more input is needed
 int numerator=0;
 int denominator=0;
 int result=0;

 do
 {
    try // 读取被除数（整数）
    {
       System.out.print("请输入被除数： ");
       numerator = scanner.nextInt();
       continueLoop = false; // 正确读取到被除数，跳出while循环
    }
    //如果用户输入不是整数，则抛出inputMismatchException（输入不匹配异常）
    catch (InputMismatchException inputMismatchException)
    {
       System.err.printf("%n发生异常：%s%n",
          inputMismatchException);
       System.out.printf(
               "输入非法，请输入一个整数：%n%n");
       scanner.nextLine(); // discard input so user can try again

        }
 } while (continueLoop); 

continueLoop = true;//重置循环标记
 do
 {
    try // 读取除数（非零整数）
    {
       System.out.print("请输入除数：");
       denominator = scanner.nextInt();
       result = quotient(numerator, denominator);
       System.out.printf("%n计算结果： %d除以%d = %d%n", numerator,
          denominator, result);
       continueLoop = false; // input successful; end looping
    }
    catch (InputMismatchException inputMismatchException)
    {
       System.err.printf("%n发生异常：%s%n",
          inputMismatchException);
       scanner.nextLine(); // discard input so user can try again
       System.out.printf(
               "输入非法，请输入一个整数：%n%n");
        }
    catch (ArithmeticException arithmeticException)
    {
       System.err.printf("%n发生异常：%s%n", arithmeticException);
       System.out.printf(
          "整数除法中，除数不能为零，请重新输入！%n%n");
    } 
 } while (continueLoop); 
} 
} // end class DivideByZeroWithExceptionHandling

运行结果：

请输入被除数： a

发生异常：java.util.InputMismatchException
输入非法，请输入一个整数：

请输入被除数： 11.1

发生异常：java.util.InputMismatchException
输入非法，请输入一个整数：

请输入被除数： 88
请输入除数：b

发生异常：java.util.InputMismatchException
输入非法，请输入一个整数：

请输入除数：0

发生异常：java.lang.ArithmeticException: / by zero
整数除法中，除数不能为零，请重新输入！

请输入除数：11

计算结果： 88除以11 = 8

参考：

原代码如下：

package example;

//Fig. 11.3: DivideByZeroWithExceptionHandling.java
//Handling ArithmeticExceptions and InputMismatchExceptions.
import java.util.InputMismatchException;
import java.util.Scanner;

public class DivideByZeroWithExceptionHandling
{
// demonstrates throwing an exception when a divide-by-zero occurs
public static int quotient(int numerator, int denominator)
   throws ArithmeticException
{
   return numerator / denominator; // possible division by zero
} 

public static void main(String[] args)
{
   Scanner scanner = new Scanner(System.in); 
   boolean continueLoop = true; // determines if more input is needed

   do
   {
      try // read two numbers and calculate quotient
      {
         System.out.print("Please enter an integer numerator: ");
         int numerator = scanner.nextInt();
         System.out.print("Please enter an integer denominator: ");
         int denominator = scanner.nextInt();

         int result = quotient(numerator, denominator);
         System.out.printf("%nResult: %d / %d = %d%n", numerator,
            denominator, result);
         continueLoop = false; // input successful; end looping
      }
      catch (InputMismatchException inputMismatchException)
      {
         System.err.printf("%nException: %s%n",
            inputMismatchException);
         scanner.nextLine(); // discard input so user can try again
         System.out.printf(
                 "You must enter integers. Please try again.%n%n");
          }
      catch (ArithmeticException arithmeticException)
      {
         System.err.printf("%nException: %s%n", arithmeticException);
         System.out.printf(
            "Zero is an invalid denominator. Please try again.%n%n");
      } 
   } while (continueLoop); 
} 
} // end class DivideByZeroWithExceptionHandling

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Java源码-第一个异常处理小程序：整数除法

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