This code snippet about final keyword in java. As a intro - We can use final keyword to variable then that variable become constant and if we use final keyword to a method that method cannot override and if we use for class that class stop inheriting.

FinalKeyword.java

class Father {
	//delete final to get rid from error
	public final void doingNow(){
		System.out.println("reading book");
	}
	
	
	
}

//final class cannot have child classes
//delete final to get rid from error
final class Son extends Father{
	//final method cannot override
	//overridden method
	public void doingNow(){
		System.out.println("Watchin TV");
	}
	
	public static void main(String[] args) {
		//there is no point of having constant variable without initializing
		//final int WIDTH;
		
		//use upper case for constant(final) variables.
		//final int WIDTH = 30;
		
		//System.out.println(width);
		
		//example for constant variable
		//Math.PI
		
		//without final we can change value of width
		//width = 50;
		//System.out.println(width);
		
		//have to create object of this class otherwise we cannot access to a doingNow()
		//because cannot call non-statitc method in static method.
		Son firstSon = new Son();
		firstSon.doingNow();	
			
	}

}

//if we add final to son class son class cannot be a parent for grandSon class.
class grandSon extends Son{
	
	
}