try and catch block

try and catch block

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.

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.

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

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

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");
}	
}
}

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.

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");
}	
}
}

Enter any two number: 5 0
Denominator not be zero