Homework 4
(revised)

CS409 - Spring 2000

Due: Thursday, Feb 24

• The method toString() has been added to Rectangle.  You need to write this method to ensure that your Rectangle can be printed.
• A correction has been made in the code for the IllegalArgumentException below (the word "new" was omitted in the earlier version).
• The explanation of contains() has been expanded to indicate what should be done with points on the Rectangle's boundary.
• The explanation of intersect() has been expanded to indicate what should be done when Rectangles don't intersect.
• Some useful Java information has been added and some Java information that applied only to a previous version of J++ has been omitted.

This is your first assignment that involves programming.  It is meant to be a moderately easy in order to give everyone a chance to try out Java. Even though this assignment is not difficult you should start early to ensure that you have enough time to complete it.  Programming, especially when using an unfamiliar language, can be time-consuming. 

You need to create a class that implements the ADT Rectangle. Rectangle is actually a hyper-rectangle since it is supposed to work for any dimension.  Here are the operations, in Java form, that Rectangle needs to handle:

• public Rectangle (int[] lowerCorner, int[] upperCorner);
  Construct a new Rectangle.  It is an error if the corners are different dimensions.  Also each coordinate of the lower corner is supposed to be less than or equal to the corresponding coordinate of the upper corner; it is an error if this does not hold.
• public int dimension();
  Report this Rectangle's dimension.
• public boolean contains (int[] point);
  Determine whether the given point is contained within this Rectangle.  It is an error if the point is the wrong dimension.  Points on the boundary are considered to be contained within the Rectangle.
• public Rectangle intersect (Rectangle rect);
  Report the Rectangle that is the intersection of this Rectangle and rect.  If the rectangles don't intersect then null should be returned.
• public String toString ();
  Report a String representation of this Rectangle.  Any kind of reasonable and useful representation is acceptable.

Java has an extensive set of Exceptions that can be used to handle various kinds of errors.  The errors mentioned above fall into the category of IllegalArgumentException.  If such an error occurs then the following java code can be used:

throw new IllegalArgumentException("Useful info about problem");

What to turn in: We want to see two things:

1. The file containing your implementation of class Rectangle.
2. The output from a test program that uses your class.  This test program is not yet online, but when it is there will be a link to it on the HW04 Web page.

Some Useful Java Information

• Printing (to standard output) is done using System.out.println(String).
• You can see the Output window by choosing Output in the Other Windows submenu of the View menu.  You can print the contents of the Output window by clicking on it on and then selecting Print... from the File menu.
• Strings can be concatenated by using + (i.e., "a" + "bc" is the same as "abc").  An int that appears where a String is expected is automatically converted to the appropriate String.  Strings are immutable (i.e., once created they can't be changed).  If you want to add to an existing string (as you might want to do in toString(), for instance), you should use StringBuffer.  StringBuffer's append() method lets you append to an existing StringBuffer.
• A Rectangle with lower corner (0,0) and upper corner (2,1) can be created with the following code:
      new Rectangle( new int[] {0,0}, new int[] {2,1});
  Note the use of (unnamed) integer arrays.