java——第十二章 异常处理和文本I/O

1.异常处理：

使用try_throw_catch块模块

优点：将检测错误（由被调用的方法完成）从处理错误（由调用方法完成）中分离出来。

例子：

 package test;
 import java.util.Scanner;
 public class Demo {

     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 {  //try块包含正常情况下执行的代码
     int result = quotient(number1,number2);
     System.out.println(number1 + " / "+ number2 + " is "+result);
     }
     catch(ArithmeticException ex)   //异常被catch所捕获
     {
         System.out.println("Exception: an integer " + " Cannot be divided by zero ");
     }
     System.out.println("Execution continues...");
     }

     public static int quotient(int number1,int number2)
     {
         if(number2==)
         {
             throw new ArithmeticException("Divisor cannot be zero");
             //System.exit(1);//表示非正常退出程序
         }
         return number1/number2;
     }
 }

例子二：输入类型有错误，抛出异常

 package test;
 import java.util.*;//代表你导入了java.util包中的所有类,,
 public class Demo {

     public static void main(String[] args) {

     Scanner input = new Scanner(System.in);
     boolean continueInput = true;

     do {
         try {
             System.out.print("Enter an integers: ");
             int number = input.nextInt();

             System.out.println("The number entered is "+ number);
             continueInput = false;
         }
         catch(InputMismatchException ex)
         {
             System.out.println("try again.(" + "Incorrect input: an integer id=s required)");
             input.nextLine();//接受输入的一行数据 以/r为结束
         }
     }while(continueInput);
     }
 }