• Final is a Keyword.


• You can not change value of a final variable (it is a constant).


• Java class which declared as Final cannot be extended(Restricting inheritance).


• A Method declared as final cannot be overridden.

final keyword can be use in three scenario.

• Final keyword with variables - means that variable become constant that is no one can change the value of variable.
  Example - final int num=10;


• Final keyword with methods - means that method will not be overridden by other class.
  Example - fianl void print(){}


• Final keyword with classes - means that class will not inherit by other class.
  Example - final class Demo{}

Final Variable:-

• Java uses the "final" modifier to declare constants.


• The "const" modifier will be applicable only to non-primitive types. The primitive types should continue to use the modifier "final".

Example :

public class Final1 {
final int var=10;
     
void display()
 {
	 var=15;
 }
	public static void main(String[] args) {
Final1 f=new Final1();
System.out.println(" final var Cannot be modify");
f.display();

	}

}

Output :

final var Cannot be modify
Exception in thread "main" java.lang.Error: Unresolved compilation problem

Final Method :

Note : Method cannot be overridden.

class Final1 {
	final void display()
	{
		System.out.println("Display Final Method");
	}
	
}
class Final2 extends Final1
{
	 void display()
	{
		System.out.println("Display Final Method");
	}
	public static void main(String args[]) {
		Final2 f= new Final2();
		System.out.println("Displaying Error");
		f.display();
		
	}
}

Output :

Compile Time Error

Final Class :

Note : Java class which declared as Final cannot be extended.

Example :

final class Final1
{
	
}
class Final2 extends Final1
{
	void display()
	{
	 System.out.println(" Final Class");
	}
	public static void main(String[] args) {
		Final2 f=new Final2();
		f.display();
	}
}

Output :

Compile Time Error