java异常处理

浏览数：16 / 时间：2015年06月08日

1、异常处理概述

从一个读取两个整数并显示商的例子：

    public static void main(String args[])
    {
        Scanner input = new Scanner(System.in);
        
        System.out.print("Enter two integers: ");
        int number1 = input.nextInt();
        int number2 = input.nextInt();
        
        System.out.println(number1 + " / " + number2 + " is " + (number1 / number2));
    }

Enter two integers: 3 0
Exception in thread "main" java.lang.ArithmeticException: / by zero
at Main.main(Main.java:18)

解决的一个简单的办法是添加一个if语句来测试第二个数字：

public class Main
{
    public static void main(String args[])
    {
        Scanner input = new Scanner(System.in);
        
        System.out.print("Enter two integers: ");
        int number1 = input.nextInt();
        int number2 = input.nextInt();
        if(number2 != 0)
            System.out.println(number1 + " / " + number2 + " is " + (number1 / number2));
        else
            System.out.println("Divisor cannot be zero ");
    }
}

为了演示异常处理的概念，包括如何创建、抛出、捕获以及处理异常，继续改写上面的程序如下：

public class Main
{
    public static void main(String args[])
    {
        Scanner input = new Scanner(System.in);
        
        System.out.print("Enter two integers: ");
        int number1 = input.nextInt();
        int number2 = input.nextInt();
        try {
            if(number2 == 0)
                throw new ArithmeticException("Divisor cannot be zero");
            System.out.println(number1 + " / " + number2 + " is " + (number1 / number2));
        }
        catch(ArithmeticException ex) {
            System.out.println("Exception: an integer " + "cannot be divided by zero ");
        }
        System.out.println("Execution continues ...");
    }
}

2、异常处理的优势

改用方法来计算商：

public class Main
{
    public static int quotient(int number1, int number2) {
        if(number2 == 0)
            throw new ArithmeticException("Divisor cannot be zero");
        return number1 / number2;
    }
    
    public static void main(String args[])
    {
        Scanner input = new Scanner(System.in);
        
        System.out.print("Enter two integers: ");
        int number1 = input.nextInt();
        int number2 = input.nextInt();
        try {
            int result = quotient(number1, number2);
            System.out.println(number1 + " / " + number2 + " is " + result);
        }
        catch(ArithmeticException ex) {
            System.out.println("Exception: an integer " + "cannot be divided by zero ");
        }
        System.out.println("Execution continues ...");
    }
}