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Tuesday, 29 January 2013

what is|define|Definition of exception handling mechanism in java with sample|example program|interview questions and answers on|pdf|ppt|tutorial best partices


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    Exception Handling:

      
     Defintion Of Exception Handling:

           An Exception is an object occurred at Run time Which Describes A Nature of the 
    message.the nature of the message can be either System Error Message or User Friendly 
    Error Message.

      For Example:

              ArithmeticException ae=new ArithmeticException(“div By Zero”);

               Div by zero -------> Nature Of the Message.
              ae------------------> Object of the Arithmetic Exception.

      Handling the Exceptions:

          Handling the Exceptions are nothing but converting System Error Messages into User 
      Friendly error Messages.
      Handling the exceptions are of two types. They are
    1)   By using predefined exception process
    2)   User defined Exception Handling

     1) By using predefined Exception process:


          To Handle the exception process we have five keywords they are.
     1) try
     2) catch
     3) finally
     4) throws
     5) throw

       Syntax :

        try
      {
         // Block of Statements
        // Which causes errors at runtime
       }

      Catch(ExceptionType1 obj1)
     {
       //Block Of Stmts
      // Which Provides user friendly error mssg
     }

      Catch(ExceptionType2 obj2)
    {
       //Block Of Stmts
      // Which Provides user friendly error mssg
     }
      ………………..
       ……………….

     Catch(ExceptionTypen objn)
    { 
      //Block Of Stmts
     // Which Provides user friendly error mssg
    }
     Finally
   {
    }

     1) try:

        It is One of the block contains the block of statements which Causes problematic 
     Statements.

     2) Catch():

          It is one of the block in which we write block of statements. Which will provide User  
     Friendly Messages i.e; It suppress System Errors Messages And Generates User friendly 
     messages. If Any Exception Is Occurred then appropriate catch block is executed.

     3) Finally:
         It is one of the block contains block of statements which will perform relinquish  
   (close/terminate) resources which are obtained in try block.

     4) throws :
          Throws is keyword which always gives an indication of specific Method (calling function) 
     to place common exception methods(Called Functions)
                                                                     OR
        Throws is keyword which will express or describes the exceptions which are occurring as 
    part of common method Body.

     Syntax:

           Returntype MethodName(listof formalparameters)throws                 
            exceptiontype1,exceptiontope2……….exceptiontypeN
         {
             //Block of Statements;
          }

Exception Handling
           

    5) Throw:
       Throw is Keyword Used for Raising or generating the Exception Which Are occurring as 
     part of method Body.

                                                         OR
       Throw is Keyword Which Carrying The Created Exception From Method body to Method 
    Heading and Handovers to throws Keyword.

     Syntax:

        <classname> <objname>=new <classname>(obj);
        Throw(obj);



 
  

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