Eric S. Roberts Stanford University Stanford, California January 2006
This text is an early draft for a general introductory textbook in computer science—a Java-based version of my 1995 textbook The Art and Science of C. My hope is that I can use much of the existing material in writing the new book, although quite a bit of the material and overall organization have to change. At this point, the material is still in a preliminary form, and the feedback I get from those of you who are taking this course will almost certainly lead to some changes before the book is published. One of the central features of the text is that it incorporates the work of the Association of Computing Machinery’s Java Task Force, which was convened in 2004 with the following charter: To review the Java language, APIs, and tools from the perspective of introductory computing education and to develop a stable collection of pedagogical resources that will make it easier to teach Java to first-year computing students without having those students overwhelmed by its complexity.
I am grateful to my colleagues on the Task Force—Kim Bruce, Robb Cutler, James H. Cross II, Scott Grissom, Karl Klee, Susan Rodger, Fran Trees, Ian Utting, and Frank Yellin—for all their hard work over the past year, as well as to the National Science Foundation, the ACM Education Board, the SIGCSE Special Projects Fund for their financial support. I also want to thank the participants in last year’s CS 298 seminar—Andrew Adams, Andy Aymeloglu, Kurt Berglund, Seyed Dorminani-Tabatabaei, Erik Forslin, Alex Himel, Tom Hurlbutt, Dave Myszewski, Ann Pan, Vishakha Parvate, Cynthia Wang, Paul Wilkins, and Julie Zhuo for helping me work through these ideas. In addition, I would like to thank my CS 106A TA Brandon Burr and all the hardworking section-leaders for taking on the challenge of helping to teach a course with a just-in-time approach to the materials. Particularly because my wife Lauren Rusk (who has edited all of my books) has not yet had her chance to work her wonderful magic on the language, you may still find some rough edges, awkward constructions, and places where real improvement is needed. Writing is, after all, at least as difficult as programming and requires just as much testing to get everything right. If you let me know when things are wrong, I think we’ll end up with a textbook and a course that are exciting, thorough, and practical. Thanks in advance for all your help. Eric Roberts Professor of Computer Science Stanford University September 2005
Table of Contents
1. Introduction 1 1.1 A brief history of computing 2 1.2 What is computer science? 4 1.3 An overview of computer hardware 5 1.4 Algorithms 7 1.5 Stages in the programming process 8 1.6 Java and the object-oriented paradigm 13 1.7 Java and the World Wide Web 17 2. Programming by Example 21 2.1 The “hello world” program 22 2.2 Perspectives on the programming process 2.3 A program to add two numbers 26 2.4 Classes and objects 31 3. Expressions 39 3.1 Primitive data types 41 3.2 Constants and variables 42 3.3 Operators and operands 46 3.4 Assignment statements 53 3.5 Programming idioms and patterns 4. Statement Forms 63 4.1 Simple statements 64 4.2 Control statements 66 4.3 Boolean data 67 4.4 The if statement 73 4.5 The switch statement 78 4.6 The concept of iteration 79 4.7 The while statement 85 4.8 The for statement 90 5. Methods 99 5.1 A quick overview of methods 100 5.2 Methods and the object-oriented paradigm 5.3 Writing your own methods 108 5.4 Mechanics of the method-calling process 5.5 Algorithmic methods 125
6. Objects and Classes 135 136 6.1 Using the RandomGenerator class 6.2 Defining your own classes 143 6.3 Defining a class to represent rational numbers 7. The Object Memory Model 165 7.1 The structure of memory 166 7.2 Allocation of memory to variables 7.3 Primitive types vs. objects 176 7.4...