What is the purpose of the final keyword in Java?

The final keyword in Java is used to declare a variable, method or class as a constant, which cannot be changed or overridden by the program.

If a variable is declared as final, its value cannot be changed after it is initialized. Similarly, if a method is declared as final, it cannot be overridden by a subclass, and if a class is declared as final, it cannot be subclassed.

The main purpose of using final is to prevent the accidental modification of a variable or method, which could lead to bugs in the program. It also allows the programmer to create constants that can be used throughout the program without worrying about their values being changed.

Additionally, using final can also help the compiler optimize the code, as it can assume that the value of a final variable or method will not change during runtime and optimize accordingly.