Created by a professor of computer science at Hobart and William Smith Colleges, this online textbook "is suitable for use in an introductory programming course and for people who are trying to learn programming on their own." The free resource uses Java as a basis for discussing principles of data types, subroutines, and other program characteristics that are similarly handled in most common programming languages. Additionally, many topics that are specific to the Java platform are addressed, and the author has developed a number of Java applets that demonstrate underlying concepts.