Exception handling in Java

Exception handling in Java

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  Exceptions Mr.PrasadSawantDepartmentOf Computer ScienceProf .Ramkurshana More Arts, Commerce and Science College Akurdi. Mobile :9665755707 Email:sawanprasad@gmail.comBlog:http://prasadmsawant.blogspot.com/
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  Agenda Define exception.Discusswhat 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.
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  What is exception?Whenan error is encountered during the execution of a program an exception is said to have occurred.
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  Handling Exception…IF B IS ZERO GO TO ERORC=A/BPRINT CGO TO EXIT ERROR: DISPLAY “CODE CAUSING ERROR DUE TO DIVISION BY ZERO”EXIT:ENDBLOCK THAT HANDLES ERROR
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  HANDLING EXCEPTION INJAVA OBJECTErrorTHROWABLEExceptionSQLExceptionAWT ERRORClassNotFoundExceptionThread Death..………………
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  System-Defined ExceptionRaised implicitlyby system because of illegal execution of program When cannot continue program execution any more Created by Java System automatically Exception extended from Error class and RuntimeException class [DivByZero.java] IndexOutOfBoundsException: When beyond the bound of index in the object which use index, such as array, string, and vector ArrayStoreException : When assign object of incorrect type to element of array NegativeArraySizeException : When using a negative size of array NullPointerException :When refer to object as a null pointerSecurityException : When violate security. Caused by security managerIllegalMonitorStateException : When the thread which is not owner of monitor involves wait or notify method
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  Programmer-Defined Exception Exceptionsraised by programmer Check by compiler whether the exception handler for exception occurred exists or notIf there is no handler, it is error Sub class of Exception class
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  The exception handlingmodeltry { // 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 */}
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  Multiple catch blockClasscatch22{ 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 aNot a numberC:>javac catch22 3The squre is 9
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  Nested try-catch …try{intnum=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 aNot a numberC:>javac catch22 3The squre is 9
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  Finally blockThe ‘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 blockNo exceptionExceptionfinallyCatch blockfinally
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  Using throws andthrowException 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.