1. Exceptions Mr.PrasadSawantDepartment Of Computer ScienceProf .Ramkurshana More Arts, Commerce and Science College Akurdi. Mobile :9665755707 Email:sawanprasad@gmail.comBlog:http://prasadmsawant.blogspot.com/
2. Agenda Define exception. Discuss what is meant by exception handing. Describe the try,catch and finally blocks. Examine multiple catch blocks. Explore nested try catch blocks. Explain the use of throw and throws keywords. Create user defined exception.
3. What is exception? When an error is encountered during the execution of a program an exception is said to have occurred.
4. Handling Exception … IF B IS ZERO GO TO EROR C=A/B PRINT C GO TO EXIT ERROR: DISPLAY “CODE CAUSING ERROR DUE TO DIVISION BY ZERO” EXIT: END BLOCK THAT HANDLES ERROR
7. Programmer-Defined Exception Exceptions raised by programmer Check by compiler whether the exception handler for exception occurred exists or not If there is no handler, it is error Sub class of Exception class
8. The exception handling model try { // code which is expected to throw an exception } Catch (exception e1) { /* If exception is thrown in the try block ,is of type e1,then perform necessary action here */ }
9. Multiple catch block Class catch22 { public static void main(String args[]) { try { String num=args[0]; intnumValue=Interger.parseInt(num); System.out.println(“The squre is ”+numValue*numvalue”); } catch(ArrayIndexOutOfBoundException e1) { System.out.println(“No argument is given!”); } catch(NumberFormatException e2) { System.out.println(“Not a number “); } } } C:>javac catch22 No argument is given! C:>javac catch22 a Not a number C:>javac catch22 3 The squre is 9
10. Nested try-catch … try { int num=args.length; try { intnumValue=Integer.parseInt(args[0]); System.out.println(“The squre is “+numValue*numValue); } catch(NumberFormatExcption e1) { System.out.println(“Not a Number!”); } } catch (ArrayIndexOutOfBoundException e2) { System.out.println(“No arguments given!”); } …. C:>javac catch No argument is given! C:>javac catch22 a Not a number C:>javac catch22 3 The squre is 9
11. Finally block The ‘finally ’block is guaranteed to run whether or not an exception occurs. The finally clauses of a try catch block will always execute ,even if there are return statement in the try catch part . Try block No exception Exception finally Catch block finally
12. Using throws and throw Exception are thrown with the help of the ‘throw’ keyword .The ‘throw’ keyword is used to indicate that an exception has occurred .The operand of throw is an object of any class that is derived from the class ’Throwable’. The throws keyword is used to list the exception that method can throw.
