final Keyword in Java

The final keyword in Java is a non-access modifier that can be used with variables, methods, and classes. It prevents the value of a variable, the behavior of a method, or the structure of a class from being changed.

Use case of final keyword in Java

The final keyword can be used in Java in three ways:

• To declare constants. A final variable can only be assigned once, and its value cannot be changed after that. This makes it useful for declaring constants, such as PI or the number of seconds in a minute.
• To prevent methods from being overridden. A final method cannot be overridden by a subclass. This is useful for methods that are part of a class’s public API and should not be modified by subclasses.
• To prevent classes from being inherited from. A final class cannot be inherited from by a subclass. This is useful for classes that should not be extended, such as the String class.

Why use final keyword in Java?

There are several reasons why we might want to use the final keyword in Java:

• To improve code readability and maintainability. The final keyword can make our code more readable and maintainable by making it clear which variables and methods cannot be changed.
• To prevent errors. The final keyword can help to prevent errors by preventing variables and methods from being changed in ways that could cause problems.
• To enforce design decisions. The final keyword can be used to enforce design decisions, such as ensuring that a class cannot be extended or that a method cannot be overridden.

The final keyword and constants

To declare a final variable, we simply add the final keyword to the variable declaration.

For example:

final int MAX_VALUE = 100;

This declares a final variable named MAX_VALUE that is initialized to the value 100 and it cannot be changed after it is initialized.

A constant is a value that is fixed. We can create constants in Java using the final keyword. In the above example, the MAX_VALUE is also a constant.

The final keyword and methods

To declare a final method, we add the final keyword to the method declaration.

For example:

final void printHello() {
  System.out.println("Hello!");
}

This declares a final method named printHello() that prints the message “Hello!”. The printHello() method cannot be overridden by a subclass. If we try to override this method the compiler will show an error.

The final keyword and classes

To declare a final class, we add the final keyword to the class declaration.

For example:

final class Point {
  int x;
  int y;

  Point(int x, int y) {
    this.x = x;
    this.y = y;
  }
}

This declares a final class named Point that has two fields, x and y. The Point class cannot be inherited from by a subclass.

When a class is declared as final, it cannot be subclassed. This means that no other class can inherit from the final class.

Summary of the key points

• The final keyword in Java is a non-access modifier that can be used with variables, methods, and classes.
• The final keyword can be used to declare constants, prevent methods from being overridden, and prevent classes from being inherited from.
• There are several reasons why we might want to use the final keyword in Java, including improving code readability and maintainability, preventing errors, and enforcing design decisions.

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