10.16 ppt作业

//课堂测试
package test01;

import java.util.Scanner;

public class Main{

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(true){
            try{
                String s = scanner.next();
                int num = Integer.parseInt(s);
                int flag = 0;
                if(num>=90&&num<=100){
                    flag = 1;
                }
                else if(num>=80&&num<90){
                    flag = 2;
                }
                else if(num>=70&&num<80){
                    flag = 3;
                }
                else if(num>=60&&num<70){
                    flag = 4;
                }
                else if(num>=0&&num<60){
                    flag = 5;
                }
                else{
                    flag = 0;
                }
                switch(flag){
                    case 1:
                        System.out.println("优");
                        break;
                    case 2:
                        System.out.println("良");
                        break;
                    case 3:
                        System.out.println("中");
                        break;
                    case 4:
                        System.out.println("及格");
                        break;
                    case 5:
                        System.out.println("不及格");
                        break;
                    default:
                        System.out.println("Error!");
                        break;
                }
            }
            catch(Exception e){
                System.out.println("Error!");
            }
        }


    }
}

//动手动脑
import javax.swing.*;

class AboutException {
    public static void main(String[] a)
    {
        int i=1, j=0, k;
        k=i/j;
        try
        {

            k = i/j;    // Causes division-by-zero exception
            //throw new Exception("Hello.Exception!");
        }

        catch ( ArithmeticException e)
        {
            System.out.println("被0除.  "+ e.getMessage());
        }

        catch (Exception e)
        {
            if (e instanceof ArithmeticException)
                System.out.println("被0除");
            else
            {
                System.out.println(e.getMessage());

            }
        }
        finally
        {
            JOptionPane.showConfirmDialog(null,"OK");
        }
    }
}
//Exception in thread "main" java.lang.ArithmeticException: / by zero at AboutException.main(Main.java:7)

//浮点数除以0
public class ThrowDemo {
    public static void main(String[] args) {
//        try {
        double data = 100 / 0.0;
        System.out.println("浮点数除以零：" + data);
//            if(String.valueOf(data).equals("Infinity"))
//            { 
//                System.out.println("In Here" ); 
//                throw new ArithmeticException("除零异常");
//            }
//        } 
//        catch(ArithmeticException e) { 
//            System.out.println(e); 
//        } 
    }
}
//结果如下：
//浮点数除以零：Infinity（随机赋值一个值）

//CatchWho.java
public class CatchWho {
    public static void main(String[] args) {
        try {
            try {
                throw new ArrayIndexOutOfBoundsException();
            }
            catch(ArrayIndexOutOfBoundsException e) {
                System.out.println(  "ArrayIndexOutOfBoundsException" +  "/内层try-catch");
            }

            throw new ArithmeticException();
        }
        catch(ArithmeticException e) {
            System.out.println("发生ArithmeticException");
        }
        catch(ArrayIndexOutOfBoundsException e) {
            System.out.println(  "ArrayIndexOutOfBoundsException" + "/外层try-catch");
        }
    }
}
//结果如下：
//ArrayIndexOutOfBoundsException/内层try-catch
//发生ArithmeticException

//CatchWho2.java
public class CatchWho2 {
    public static void main(String[] args) {
        try {
            try {
                throw new ArrayIndexOutOfBoundsException();
            }
            catch(ArithmeticException e) {
                System.out.println( "ArrayIndexOutOfBoundsException" + "/内层try-catch");
            }
            throw new ArithmeticException();
        }
        catch(ArithmeticException e) {
            System.out.println("发生ArithmeticException");
        }
        catch(ArrayIndexOutOfBoundsException e) {
            System.out.println( "ArrayIndexOutOfBoundsException" + "/外层try-catch");
        }
    }
}

//结果如下：
//ArrayIndexOutOfBoundsException/外层try-catch

package test01;

public class EmbededFinally {
    
    public static void main(String args[]) {
        int result;
        try {
            System.out.println("in Level 1");
            try {
                System.out.println("in Level 2");
                // result=100/0;  //Level 2
                try {
                    System.out.println("in Level 3");
                    result=100/0;  //Level 3
                }

                catch (Exception e) {
                    System.out.println("Level 3:" + e.getClass().toString());
                }

                finally {
                    System.out.println("In Level 3 finally");
                }
                // result=100/0;  //Level 2
            }

            catch (Exception e) {
                System.out.println("Level 2:" + e.getClass().toString());
            }
            finally {
                System.out.println("In Level 2 finally");
            }
            // result = 100 / 0;  //level 1
        }
        catch (Exception e) {
            System.out.println("Level 1:" + e.getClass().toString());
        }
        finally {
            System.out.println("In Level 1 finally");
        }

    }

}
//结果如下：
/*
in Level 1
in Level 2
in Level 3
Level 3:class java.lang.ArithmeticException
In Level 3 finally
In Level 2 finally
In Level 1 finally
*/
    
    
package test01;

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");
        }
    }
}
//结果如下：
/*
in main
Exception is thrown in main
并没有实现finally中的语句，因为System.exit(0);强制程序退出了
*/