More about Objects and Classes

4. Multiple Constructors

Answer:
The different constructors require different parameters. 
 (Different types of data are supplied to the constructors.)

Multiple Constructors


import java.awt.*;      // import the package that contains Point
class PointEg1
{

  public static void main ( String arg[] )
  {
    Point a, b, c;              // reference variables

    a = new Point();            // create a Point at (0,  0); 
                                // save the reference in "a"
    b = new Point( 12, 45 );    // create a Point at (12, 45); 
                                // save the reference in "b"
    c = new Point( b );         // create a Point containing data equivalent
                                // to the data referenced by "b"
  }
}

Any of the three constructors can be used to create a Point. It is a matter of convenience which constructor you use. Look at the example program.

To use the definition of class Point, import the package that contains it. The statement:

import java.awt.*

says to use the AWT package that comes with Java. The * says that everything defined in the package can be used (although this program only uses the Point class).

Question 4:
Say that the program has just been loaded into main memory and is just about to start running.
How many reference variables are there?
How many objects are there?