What is the purpose of the final modifier in Java and in what situations is its use justified?

In Java, the final modifier is used for:

• Variables: the value of the variable cannot be changed after initialization.
• Methods: the method cannot be overridden in subclasses.
• Classes: the class cannot be inherited.

The use of final is justified when it is necessary to guarantee immutability of data or behavior, for example:

• Constants declared as final to protect against modification.
• Methods that should not be overridden to preserve logic.
• Classes that are not intended to be extended, such as String.

Example:

public final class Constants {
    public static final double PI = 3.1415;
}

public class Base {
    public final void doSomething() {
        // cannot be overridden
    }
}