final keyword in java

In Java, the final keyword is used to restrict the modification of a variable, method, or class. Once a variable, method, or class is declared as final, its value or implementation cannot be changed.

Here are some common uses of the final keyword in Java:

1. Final variables:
   A final variable is a constant whose value cannot be changed once it is assigned. It can be assigned a value only once, either at the time of declaration or in a constructor. For example:

final int x = 10;

2. Final methods:
   A final method is a method that cannot be overridden by a subclass. Once a method is declared as final in a superclass, its implementation cannot be changed in any subclass. For example:

public class Parent {
    public final void method() {
        // method code here
    }
}

public class Child extends Parent {
    // cannot override the Parent method
}

3. Final classes:
   A final class is a class that cannot be subclassed. Once a class is declared as final, it cannot be extended by any subclass. For example:

public final class MyClass {
    // class code here
}

public class MySubclass extends MyClass {
    // error: cannot extend final class
}

In addition to the above uses, the final keyword is also used in Java to declare constants, as well as to prevent reference variables from being reassigned.