User defined exception

Although Java’s built-in exceptions handle most common errors, but sometimes you would  probably want to create your own exception types to handle situations specific to your applications. For this  just define a subclass of Exception  which is, of course, a subclass of Throwable . Your subclasses don’t need to actually implement anything—it is their existence in the type system that allows you to use them as exceptions.

The Exception class does not define any methods of its own. But inherit those methods provided by Throwable. Thus, all exceptions, including those that you create, have the methods defined by Throwable available to them. You may also wish to override one or more of these methods in exception classes that you create.

Methods Defined by Throwable

Throwable	fillInStackTrace()           Fills in the execution stack trace.
Throwable	getCause()           Returns the cause of this throwable or null if the cause is nonexistent or unknown.
String	getLocalizedMessage()           Creates a localized description of this throwable.
String	getMessage()           Returns the detail message string of this throwable.
StackTraceElement[]	getStackTrace()           Provides programmatic access to the stack trace information printed by printStackTrace().
Throwable	initCause(Throwable cause)           Initializes the cause of this throwable to the specified value.
void	printStackTrace()           Prints this throwable and its backtrace to the standard error stream.
void	printStackTrace(PrintStream s)           Prints this throwable and its backtrace to the specified print stream.
void	printStackTrace(PrintWriter s)           Prints this throwable and its backtrace to the specified print writer.
void	setStackTrace(StackTraceElement[] stackTrace)           Sets the stack trace elements that will be returned by getStackTrace() and printed by printStackTrace() and related methods.
String	toString()           Returns a short description of this throwable.

Example

// Demonstrate user defined exception

class MyException extends Exception

{

       private int x;

       MyException(int a)

       {

           x=a;

                 }

       public String toString()

                {

                     return("MyException [ " + x + "]");

                 }

}

class ExceptionDemo1

 {

     static void compute(int a) throws MyException

     {

         System.out.println(" called compute : "+a);

         if(a>10)

                  throw new MyException(a);

        System.out.println("Exit");

     }

       

public static void main(String args[])

  {

     try

       {

           compute(11);

       }

     catch(MyException e)

          {

                System.out.println("Error : "+e);

          }

}

}

Posted by: Ruchita Pandya