Using finally

Using finally

• Sometimes because of execution of try block the execution gets break off. And due to this some important code (which comes after throwing off an exception) may not get executed. That means, sometimes try block: may bring some unwanted things to happen.

• The finally block provides the assurance of execution of some important code that must be executed after the try block.

• Even though there is any exception in the try block the statements assured by finally block are sure to execute. These statements are sometimes called as clean up code. The syntax of finally block is

finally {

//clean up code that has to be executed finally

}

The finally block always executes. The finally block is to free the resources.

Java Program [finallyDemo.java]

/*

This is a java program which shows the use of finally block for handling exception */

class finallyDemo

{

public static void main(String args[])

{

int a 10,b=-1;

try

{

b=a/0;

}

catch(ArithmeticException e)

{

System.out.println("In catch block: "+e);

}

finally

{

if(b!= -1)

System.out.println("Finally block executes without occurrence of exception");

else

System.out.println("Finally block executes on occurrence of exception");

}

}

}

Output

In catch block: java.lang.ArithmeticException: /by zero

Finally block executes on occurrence of exception

Program Explanation

• In above program, on occurrence of exception in try block the control goes to catch block, the exception of instance ArithmeticException gets caught. This is divide by zero exception and therefore /by zero will be printed as output. Following are the rules for using try, catch and finally block

1. There should be some preceding try block for catch or finally block. Only catch block or only finally block without preceding try block is not at all possible.

2. There can be zero or more catch blocks for each try block but there must be single finally block present at the end.