exception handling
- 1. EXCEPTION HANDLING Submitted by D.Shanmugapriya II-Msc(IT) Department of CS & IT Nadar Saraswathi college of Arts & Science Theni.
- 2. Contents • Errors and Exception • Exception Handling Mechanism • Try,catch and throw • Re-throwing an exception • Specifying Exceptions
- 3. What is an Error? • An Error is a term used to describe any issue that arises unexpectedly and results in incorrect output What are the Different types of errors? Logical error: • Occur due to poor understanding of problem or solution procedure. Syntatic error: • Arise due to poor understanding of the language itself. What is an exception? • Exception are runtime anomalies or unusual conditions that a program may encounter while executing.
- 4. Exception Handling • Exceptions are of two types: • Synchronous exceptions • The exceptions which occur during the program execution due to some fault in the input data are known as synchronous exceptions. • For example:errors such as out of range, overflow,underflow. • Asynchronous exceptions • The exceptions caused by events or faults unrelated to the program and beyond the control of the program are called asynchronous exceptions. • Example:errors such as keyboard interrupts hardware malfunctions,disk failure.
- 5. Exception Handling Mechanism • Exception handling Mechanism provides a means to detect and report an exception circumstances. • Find the problem (hit the exception) • Inform that an Error has occurred (throw the exception) • Receive the error information (catch the exception) • Take corrective Actions(handle the exception)
- 6. Types of Exception Handling • The exception handling mechanism is bulit upon three keywords: • TRY • Is used to perface a block of statements which may generate exception. • THROW • When an exception is detected,it is thrown using a throw statement in the try block. • CATCH • A catch block defined by the keyword catch catches the exception thrown by the throw statement in the try block and handles it appropriately.
- 7. Exception thrown by functions • Int main() • { • Try • { • Divide(10,20,30); • Divide (10,10,20); • } • Catch(int I) • { • Cout <<“n exception caught”; • } • Return 0; 1.Throw point Function that causes an exception 2.Try block Invokes a function that contains an exception 3.Catch block Catches and handles the exception
- 8. Throwing mechanism • When an exception is desired to be handled is detected,it is thrown using the throw statement. • Throw statement has one of the following forms: • Throw (exception) • Throw exception • Throw; • The operand object exception may be of any type, including constants.
- 9. Multiple catch statements • Multiple catch statements can be associated with a try block. • When an exception is thrown,the exception handlers are searched for an appropriate match. • The first handler that yields the match is executed. • After executed the handler,the controls goes to the first statement after the last catch block for that try.
- 10. Multiple catch statements Int main() { Cout<<“n x ==1”; Test(1); Cout<<“n x==0”; Test(0); Cout<<“n x==-1”; Test(-1); Cout<<“n x==2”; Test(2); Return 0; }
- 11. Catching mechanism • The type indicates the type of exception that catch block handles. • The catch statement catches an exception whose type matches with the type of catch argument. A catch block like a function definition Catch(type arg) { //Statements for managing exceptions. }
- 12. Catch all Exception • A catch statement can also force to catch all Exception instead of a certain type alone. • Int main() • { • Cout<<“n testing generic catch”; • Test(1); • Test(0); • Test(-1); • Test(2); • Return 0; • }
- 13. Re-throwing exception • A handler can rethrow the exception caught without processing it. • This can be done using throw without any argument. • Here the current exception is thrown to the next enclosing try/catch block. • Every time when an exception is re-thrown it will not be caught by the same catch statements rather it will be caught by the catch statement outside the try catch block.
- 14. Thank you