What is the final keyword in Java?

Answer 1

The final keyword precedes a declared constant which after Instantiation cannot be modified.

Examples.

final double PI = 3.14;

PI = 1234; // does not compile

//or

final double ONE;

ONE = 1; // Instantiated

ONE = 2; // does not compile

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final keyword can also apply to a method or a class.

When applied to a method - it means the method cannot be over-ridden.

Specially useful when a method assigns a state that should not be changed

in the classes that inherit it, and should use it as it is (not change the method behaviour).

When applied to a class it means that the class cannot be instantiated.

A common use is for a class that only allows static methods as entry points

or static final constants - to be accessed without a class instance.

A good example is Java's:

public final class Math extends Object