10.27 动手动脑5

处理异常机制

异常的多态特性

public class SystemExitAndFinally
{
 
    public static void main(String[] args)
     
    {
         
        try
        {
 
            System.out.println("in main");
             
            throw new Exception("Exception is thrown in main");
 
                    //System.exit(0);
 
        }
         
        catch(Exception e)
 
            {
             
            System.out.println(e.getMessage());
             
            System.exit(0);
         
        }
         
        finally
         
        {
             
            System.out.println("in finally");
         
        }
     
    }
 
}

运行结果：

finally不会每次都执行，例如以上程序，当执行完throw new Exception("Exception is thrown in main");语句后便关闭了程序，System.exit(0)可以终止程序。

编写一个程序，此程序在运行时要求用户输入一个整数，代表某门课的考试成绩，程序接着给出“不及格”、“及格”、“中”、“良”、“优”的结论。

package Test;
import java.util.InputMismatchException;
import java.util.Scanner;
public class dengji {
 
    public static void main(String[] args) {
         
        Scanner scanner=new Scanner(System.in);
        int n=-1;
        try {
            System.out.print("请输入一个范围为0~100的整数:");
            n=scanner.nextInt();
            if(0<=n&&n<60){
                System.out.println("不及格");
            }
            if(60<=n&&n<80) {
                System.out.println("中");
            }
            if(80<=n&&n<90) {
                System.out.println("良");
            }
            if(90<=n&&n<=100) {
                System.out.println("优");
            }
            if(n<0||n>100) {
               System.out.println("输入超出范围！");
            }
        }
        catch (InputMismatchException e)
        {
            System.out.println("输入不是整数");
        }
 
    }
 
}