Using try, catch and finally

    Java uses the keyword tryto preface a block of code that is likely to cause an error condition and “throws” an exception.

    A catch block defined by the keyword catch “catches” the exception “thrown” by the try block and handles it appropriately.

    The catch block is added immediately after the try block as shown below:

……..

……..

try

{

   Statement; //Generate an exception

}
catch (Exception-type e)

{

   Statement; //processes the exception

}

………

………

     The try block can have one or more statements that could generate an exception. If any statement generates an exception, the remaining statements in the block are skipped and execution jumps to the catch block that is placed next to the try block.

    Every try statement must be followed by at least one catch statement.

   The catch statement is passed a single parameter, which is reference to the exception object thrown by the try block. If the catch parameter matches with the type of exception object, then the exception is caught and statements in the catch block will be executed. Otherwise, the exception is not caught and the default exception handler will cause the execution to terminate.

   Example:

class Error

{

public static void main(String args[])

 {

int a=10,b=10,c=20,d;

try

  {

   d=c/(a-b);

  }

catch(ArithmeticExceptione)

  {

System.out.println("Arithmetic exception occurred");

  }

  d=a+b;

System.out.println("D = "+d);

 }

}

Output:

Arithmetic exception occurred

D = 20

    Using Finally Statement:

o   Java supports finally statement that can be used to handle an exception that is not caught by any of the previous catch statements.

o   finallyblock can be used to handle any exception generated within the try block.

o   It may be added immediately after the try block or after the last catch block as shown below:

try                                                       try{

{                                                          ……

  …..                                                     }    

  …..                                                    catch(…) {

}                                                            …….

finally                                                  }

{                                                           ……..

  …..finally {

  …..                                                          ……

}                                                            }

o   When a finally block is defined, this is guaranteed to execute, regardless of whether or not any exception is thrown.

o   Example:

class Finally

{

public static void main(String args[])

 {

int a=10,b=10,c=20,d;

try

  {

   d=c/(a-b);

  }

catch(ArithmeticException e)

  {

System.out.println("Arithmetic exception occurred");

  }

finally

  {

System.out.println("Finally is executed");

  }

  d=a+b;

System.out.println("D = "+d);

 }

}

Output:

Arithmetic Exception Occurred

Finally is executed

D = 20