More about Objects and Classes

12. Changing Data inside a Point

Answer:

Just as the program is about to close, how many objects have been created ?

Six — three Point objects and three temporary String objects
How many object references are there?

Three — each referencing a Point
Has any garbage been created?

Three objects — each temporary String object

Changing Data inside a `Point`

Look again at the description of class Point, class Point. One of the methods is:

public void move( int x, int y ) ;

This method is used to change the x and the y data inside a Point object. The modifier public means that it can be used anywhere in your program; void means that it does not return a value.

This part of the description

( int x, int y )

says that when you use move, you need to supply two int parameters that give the new location of the point.

Here is the example program, modified again:


import java.awt.*;
class PointEg4
{

  public static void main ( String arg[] )
  {
    Point pt = new Point( 12, 45 );   // construct a Point
    System.out.println( pt );     

    pt.move( -13, 49 ) ;              // change the x and y in the Point
    System.out.println( pt ); 

  }
}

Here is what it writes to the screen:

java.awt.Point[x=12,y=45]
java.awt.Point[x=-13,y=49]

Question 12:
How many Point objects are created by this program?
How many temporary String objects are created by this program?