异常处理动手动脑

1.

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");
	     	}
			
	  }
	}

结果·：

 

 分析：使用catch语句，只能捕获Exception类及其子类的对象。因此，一个捕获Exception对象的catch语句块可以捕获所有“可捕获”的异常。

2

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：

 

 

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·：

 

 分析：找不到main方法，public static void main(String[] args)未定义

3.

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");
        
        }
    
    }

}

错误：

 

分析：当有多层嵌套的finally时，异常在不同的层次抛出 ，在不同的位置抛出，可能会导致不同的finally语句块执行顺序。

4.

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：

 

分析：finally语句块不一定会执行 

 5.

// UsingExceptions.java
// Demonstrating the getMessage and printStackTrace
// methods inherited into all exception classes.
public class PrintExceptionStack 
{
   public static void main( String args[] )
   {
      try 
      {
         method1();
      }
      catch ( Exception e ) 
      {
         System.err.println( e.getMessage() + "\n" );
         e.printStackTrace();
      }
   }

   public static void method1() throws Exception
   {
      method2();
   }

   public static void method2() throws Exception
   {
      method3();
   }

   public static void method3() throws Exception
   {
      throw new Exception( "Exception thrown in method3" );
   }
}

结果：