The final Keyword

Sometimes, we require a variable to not actually be a variable in Java programs. This means that the value of the variable should not change during the execution of the program. For example, if you’re using a double type variable, pi, to store the value of $\pi$, which is a mathematical constant, you wouldn’t want to accidentally update it. Thus, for situations like these, we have the keyword: final.

The final keyword

To declare an unchangeable variable, just add final before the type and name of the variable as shown here:

final type name;

You can either initialize the variable straight away by using the assignment operator. For example:

final double pi = 3.14; 

Or you can declare it first and initialize it later, as shown here:

final double pi;
pi = 3.14;

However, remember that any attempt to update the value of this variable would result in an error!

Example

Let’s say we want to write a program that calculates the circumference of the circle using the value of radius. According to the formula:

Here, $\pi$ is a mathematical constant with a value of $3.14159265359$ ≈ $3.14$.

Let’s start the coding!