Final method cannot be overridden by subclasses. This is 
used to prevent unexpected behavior from a subclass 
altering a method.

Example:

public class MyClass {
    public final void myFinalMethod() {...}

Final Variable, it can only be assigned to once and only in 
the constructor of class if variable is not a reference to 
pther object.

Example:

public class Sphere {
 
    public static final double PI = 3.141592653589793;  // 
this might as well be a constant
    public final double radius;
    public final double xpos;
    public final double ypos;
    public final double zpos;
 
    Sphere(double x, double y, double z, double r) {
         radius = r;
         xpos = x;
         ypos = y;
         zpos = z;
    }

public final methodA(){

}
u can overirde final method & final variable can reassigned 
another value & final varaiable value must be assingend at 
the time of declaration