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When dealing with exceptions in our code, sometimes we have an operation that must be executed, even if the earlier code throws an exception. In that case, we can use the finally keyword to make sure that the correct code is executed.


To understand how the finally keyword works, let’s take a look at an example:

import java.util.Scanner;
import java.lang.NumberFormatException;
import java.lang.IllegalArgumentException;

public class Finally{
  public static void main(String[] args){
    Scanner reader;
    reader = new Scanner(;
      int x = Integer.parseInt(reader.nextLine());
      if(x < 0){
        throw new IllegalArgumentException("Input must be greater than 0!");
    }catch(NumberFormatException e){
      System.out.println("Error: Must input an integer!");
    }catch(IllegalArgumentException e){
      System.out.println("Finally Block");
    System.out.println("After Try");

This program will read an integer from the terminal. If the integer is greater than or equal to 0, it will do nothing except print the “Finally Block” and “After Try” messages. However, if the input is less than 0, it will throw an IllegalArgumentException. Finally, if the input is not a number, then an InputMismatchException will be thrown and handled. In each of those cases, it will also print the “Finally Block” message.

Let’s run this program a few times and see how it works. First, we’ll provide the input “5”:

$ java Finally
Finally Block
After Try

Here, we can see that the code in the finally block always runs when the program is finished executing the statements in the try block.

Let’s run it again, this time with “-5” as the input:

$ java Finally
Input must be greater than 0!
Finally Block
After Try

Here, we can see that it prints the error message caused by the IllegalArgumentException, then proceeds to the finally block. So, even if an exception is thrown while inside of the try block, the code in the finally block is always executed once the try block and any exception handlers are finished.

Here’s one more example, this time with “abc” as the input:

$ java Finally
Error: Must input an integer!
Finally Block
After Try

Once again, we see that the code first handles the NumberFormatException, and then it will execute the code in the finally block.

In a later chapter, we’ll learn more about how to use the finally block to perform important tasks such as closing open files and making sure we don’t leave the system in an unstable state when we handle an exception.