CS 342 - 1/21/16

The layout of a Java Program

import 
extends
implements

data member/instance variable declaration

constructors

static vs. non-static methods

   for non-static methods, there exists an implicit parameter
     that is a reference to the instance being used at the
     method call.   This implicit parameter is named: this


     Assume the Point class has a method "distance from origin"

      Point pt1;
      Point pt2;

        ...

      System.out.println ( pt1.distFromOrigin () );
      System.out.println ( pt2.distFromOrigin () );

          

       class Point
       {
          int x;  // "data member" or "instance variable"
          int y;

        double distFromOrigin ()
          {
             double dist;
             int x;       // local variable 
             String y;

             dist = .....   this.x     ......   this.y  ..... ;
                       //  above uses the data member

             return dist;
          }
 
       }

Example of a static method:

       Math.pow ()   for exponentiation

   Static methods have all "additional" information passed in
     through explicit parameters

      System.out.println ( Math.pow ( 5, 3) );

The first C++ "compliers":

   Would translate the call of:

     pt1.distFromOrigin ();

  to
  
     distFromOrigin ( pt1 );

And would translate the Method signature from

    double  Point::distFromOrigin ( )

to
    double  distFromOrigin ( Point* this )




Java Graphics
   2 main librairies
       awt - Abstract Windowing Toolkit
       swing - Windowing Librries from Jave V2.0
          All swing classes start with J


    2 primary pieces:

         Component
         Container