Lecture 9 Objectives [Nov 07]prev next

MUSICAL COMPOSITION: Rachmaninoff, Piano Concerto No. 2 in C minor, as played by Arcadi Volodos

Movement I (10:06)	Movement II (09:56)	Movement III (10:06)	Movement IV (05:42)

HAVE READ:

• [164-177]

KNOW:

• The core concept of a class
• The concept of an instance variable
• The concept of a method
• Open House for CS Department to be held at 5:00 PM in Perreault Hall. Meet CS faculty, if you are a CS major. Thinking about becoming a CS major? Come by...

BE ABLE TO:

• Write a class definition to represent a coherent set of data

DAILY QUESTION:

• Write a sample class Point that represents a point (x,y) in Cartesian coordinates with instance variables x and y of type int. Provide a method output() that prints "(x, y)" to the screen (where actual values of x, y are printed). Provide a separate class, PointTest that shows how you create a Point object representing (5, 2) and have it printed to the screen.

Sample Exam Question:

Design a class Point that represents a point (x, y) in Cartesian coordinates with integer x and y. Include methods setX(int x) and setY(int y) as methods to update (respectively) the x and y values of a Point object. Include methods getX() and getY() to retrieve the values of x and y (respectively). Include a method vectorLength() which returns a double value representing the distance from the Point to the origin (0,0).

Using the Point class, write a program PointTest that instantiates a point object and modifies it to represent the point (3, 4) in the Cartesian plane. Confirm that the getX() and getY() methods work as expected. Confirm that the method vectorLength() returns 5.0 as expected. Confirm that invoking setX(2) followed by setY(2) updates the point object so its x and y values are properly changed.