final method in java

date:16/7/12
FINAL KEYWORD------->
1.final class   :    cant be extended, that means no sub class
                                declaration--:    public final class Myfinalclass
                                                             {
                                                              --------
                                                             }




2.final variable :  cant be modified,when we require any constant  in pgm thn declare tht as final

• declaration: final<var>;
• ex: public final int PI=3.145f
• it behaves as constant,means cant be changed.
• ex pgram---------final var-----------
•  package mahajava;
• 
  public class Finalclass {
     
      public final float PI=3.14f;
     
     
     
      public void display()
      {
         
          PI++;  //compilation error,cant change final var
  
          System.out.println("final variable cant be changed");
      }
  }
  
  package mahajava;
  
  public class Finalclassm {
  
      /**
       * @param args
       */
      public static void main(String[] args) {
         
          // TODO Auto-generated method stub
          Finalclass f = new Finalclass();
          f.display();
  
      }
  
  }
  
  
  
  
  
  ---------------------->
  output
  ------------------------>
  
  Exception in thread "main" java.lang.Error: Unresolved compilation problem:
      The final field Finalclass.PI cannot be assigned

3.final method  :  cant be overriden in  subclasses but can be accessed from derived classes, if  not private.

•     declaration--: public final <return type><funtn name>

                                             ex: public final void display()

•     why final ()?

          if we want to share some common functionality with derived classes  without changing its      implementation of the funtn shared then in such cases can make tht funtn as final.