Exception Handling: try and catch block

try and catch block

if you are missing Exception Handling topic then you click here.....

try block

Inside try block we write the block of statements which causes executions at run time in other words try block always contains problematic statements.

Important points about try block

·         If any exception occurs in try block then CPU controls comes out to the try block and executes appropriate catch block.

·         After executing appropriate catch block, even through we use run time statement, CPU control never goes to try block to execute the rest of the statements.

·         Each and every try block must be immediately followed by catch block that is no intermediate statements are allowed between try and catch block.

Syntax

try

{

  .....

}

/* Here no other statements are allowed

between try and catch block */

catch()

{

  ....

}

·         Each and every try block must contains at least one catch block. But it is highly recommended to write multiple catch blocks for generating multiple user friendly error messages.

·         One try block can contains another try block that is nested or inner try block can be possible.

Syntax

try

{

.......

try

{

.......

}

}

catch block

Inside catch block we write the block of statements which will generates user friendly error messages.

catch block important points

·         Catch block will execute exception occurs in try block.

·         You can write multiple catch blocks for generating multiple user friendly error messages to make your application strong. You can see below example.

·         At a time only one catch block will execute out of multiple catch blocks.

·         in catch block you declare an object of sub class and it will be internally referenced by JVM.

Example without Exception Handling

Example

class ExceptionDemo

{

public static void main(String[] args)

{

int a=10, ans=0;

ans=a/0;

System.out.println("Denominator not be zero");                         

}

}

Abnormally terminate program and give a message like below, this error message is not understandable by user so we convert this error message into user friendly error message, like "denominator not be zero".

Example of Exception Handling

Example

class ExceptionDemo

{

public static void main(String[] args)

{

int a=10, ans=0;

try

{

ans=a/0;

}

catch (Exception e)

{

System.out.println("Denominator not be zero");

}        

}

}

Output

Denominator not be zero

Multiple catch block

You can write multiple catch blocks for generating multiple user friendly error messages to make your application strong. You can see below example.

Example

import java.util.*;

class ExceptionDemo

{

public static void main(String[] args)

{

int a, b, ans=0;

Scanner s=new Scanner(System.in);

System.out.println("Enter any two numbers: ");

try

{

           a=s.nextInt();

           b=s.nextInt();

           ans=a/b;

           System.out.println("Result: "+ans);

}

catch(ArithmeticException ae)

{

System.out.println("Denominator not be zero");

}        

catch(Exception e)

{

System.out.println("Enter valid number");

}        

}

}

Output

Enter any two number: 5 0

Denominator not be zero

finally Block in Exception Handling

Inside finallyblock we write the block of statements which will relinquish (released or close or terminate) the resource (file or database) where data store permanently.

finally block important points

·         Finally block will execute compulsory

·         Writing finally block is optional.

·         You can write finally block for the entire java program

·         In some of the circumstances one can also write try and catch block in finally block.

Example

class ExceptionDemo

{

public static void main(String[] args)

{

int a=10, ans=0;

try

{

ans=a/0;

}

catch (Exception e)

{

System.out.println("Denominator not be zero");

}        

finally

{

System.out.println("I am from finally block");

}

}

}

Output

Denominator not be zero

I am from finally block

Difference Between Throw and Throws Keyword
Custom Exception in Java
Exception Classes in Java
try and catch block