Understanding the 'final' keyword in Java

Java is a versatile, object-oriented programming language known for its robustness and simplicity. One feature that it harnesses to realize these properties is the 'final' keyword. The correct use of 'final' in Java is to create a constant variable or method. In other words, once defined, the value of a final variable cannot be modified, and a final method cannot be overridden in a subclass.

Practical Application of 'Final' Keyword in Java

Let's start with some examples to clearly understand the functions of final in Java.

1. Final Variable

Suppose you have a constant value that will not change once it is initialized. In such a case, you can use the final keyword. Take 'Pi' as an example; the value of Pi is always 3.1416, irrespective of the circumstances.

final double PI = 3.1416;

Once we declare PI as a final variable, we cannot reassign it with any new value. Any attempts to do so will result in a compilation error.

2. Final Method

When we declare a method as final, it signifies that it cannot be overridden in a subclass. This is especially helpful when you want to keep the original functionality intact, without the risk of it being altered in derived classes.

public final void display() {
    System.out.println("This is a final method.");
}

In the code snippet above, the display() method is declared final. Hence, it can't be overridden in any subclass.

Best Practices Related to the 'Final' Keyword in Java

While using the 'final' keyword, it is crucial to keep some best practices in mind:

• Only declare variables and methods as final if you're certain that their values or implementation should not be allowed to change in the future. Declaring something as final could limit the flexibility of your code.
• final variables must be initialized during their declaration or in a constructor in the case of instance variables. If you forget to do so, it will lead to a compiler error.
• Class-level final variables (or 'constants') should be named using uppercase letters with words separated by underscores for better readability. For instance MAX_SPEED.

In conclusion, the 'final' keyword plays a key role in protecting the integrity of your code, providing a measure of control over variables and methods, and maintaining a high level of code hygiene in Java programming.