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Exception handling


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Exception handling

  1. 1. Exception Handling
  2. 2. What is exception ? ● An exception is an event that occurs during the execution of a program that disrupts the normal flow of instructions. ● Anything that occurs in an unexpected way is called as exception
  3. 3. Error ● These are not exceptions at all, but problems that arise beyond the control of the user or the programmer. ● Errors are typically ignored in your code because you can rarely do anything about an error.
  4. 4. Difference between Error and Exception ● An Error "indicates serious problems that a reasonable application should not try to catch.” ● An Exception "indicates conditions that a reasonable application might want to catch."
  5. 5. Why exception occurs An exception can occur for many different reasons, including the following: ● A user has entered invalid data. ● A file that needs to be opened cannot be found. ● A network connection has been lost in the middle of communications or the JVM has run out of memory. ●
  6. 6. Types of Exceptions ● Checked exceptions ● Runtime exceptions
  7. 7. Checked Exception ● A checked exception is an exception that is typically a user error or a problem that cannot be foreseen by the programmer. ● For example, if a file is to be opened, but the file cannot be found, an exception occurs. These exceptions cannot simply be ignored at the time of compilation.
  8. 8. Runtime Exception ● A runtime exception is an exception that occurs that probably could have been avoided by the programmer. ● As opposed to checked exceptions, runtime exceptions are ignored at the time of compilation.
  9. 9. Categories of exception ● In Java, it is possible to define two catergories of Exceptions and Errors. ● JVM Exceptions: - These are exceptions/errors that are exclusively or logically thrown by the JVM. ● Examples : NullPointerException, ArrayIndexOutOfBoundsException, ClassCastException, ● Programmatic exceptions: - These exceptions are thrown explicitly by the application or the API programmers ● Examples: IllegalArgumentException, IllegalStateException.
  10. 10. Advantages of exception handling ● Separating Error-Handling Code from "Regular" Code ● Grouping and Differentiating Error Types
  11. 11. Keywords to handle exceptions Exception Handling contains 5 keywords ● 1. try ● 2. catch ● 3. finally ● 4. throws ● 5. throw
  12. 12. Syntax for Exception handling try {} catch(Exception e){ } Finally{ }
  13. 13. Purpose of try, catch and finally ● The try block identifies a block of code in which an exception can occur. ● The catch block identifies a block of code, known as an exception handler, that can handle a particular type of exception. ● The finally block identifies a block of code that is guaranteed to execute, and is the right place to close files, recover resources, and otherwise clean up after the code enclosed in the try block. ●
  14. 14. Exception Hierarchy
  15. 15. Example of Exception handling
  16. 16. Sample output