Winter 2006 CISC121 - Prof. McLeod 1

Welcome to CISC121

• Prof. (Alan) McLeod – mcleod@cs.queensu.ca• Web site at:

http://www.cs.queensu.ca/home/cisc121

• All lecture notes and examples will be posted.

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WWWW

• Who: (got that already)• Where: NIC232 (Here!)• When: 9:30am Tuesday, 8:30am Thursday, and

10:30am Fridays.

• Purpose of course (Why!):– Provide a basis for upper-year computer courses built

on first year and high school programming courses.

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Labs

• TA’s: Chanchal Roy and Chris McAloney

• Section A: Tutorial 2:30, JEF102, Lab 3:30 to 5:30pm JEF157, Mondays

• Section B: Tutorial 8:30, JEF110, Lab 9:30 to 11:30am JEF157, Wednesdays

• Note – tutorial hour before lab!• Labs start next week!• There is a self-guided lab exercise posted.

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Assignments

• Five or six of them, probably.• Submit *.java files to WebCT.• Grades and comments returned to WebCT.• No group submission – one assignment per

student.• Collaboration – share ideas, not code!

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Textbook

• “Big Java” by Cay Horstman, 2nd edition.

• First edition used last year, but it does not have any coverage of Java 5.0.

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Textbook, Cont.

• “Do I gotta buy the book?”

• “Should I buy the book?”

NO

MAYBE!

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Two Possibilities

• Plan A:– You are pretty confident in your Java programming

skills, and you figure you can get extra material from the internet, if needed.

– Do really well on the assignments!– You don’t need to buy the book and you won’t pay too

much attention to the course until around midterm time, when we get into the more “conceptual” material.

• Plan B:– Not so confident!– Buy the book, attend lectures, do the lab exercises and

assignments yourself. Get help from your TA. Work!– Relax a bit after the midterm.

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Course Content (What!)

• This is not a “Java Course”! • But, we need a language to demonstrate and

practice the concepts to be discussed.

• Java is the language of choice.– A modern, platform-independent, Object-Oriented

language.– We could have used many other languages equally

well: C#, C++, VB, Delphi, Pascal, Turing, etc.

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Course Content, Cont.

• First, a review of the Java language, then:

Practical Topics Theory Topics Algorithm Topics

Coding StyleAnalysis of Complexity

Data Structures

DocumentationNumerical Storage

& ComputationRecursion

Testing & Debugging

Sorting

Assertions & Invariants

Searching

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Course Content, Cont.

• These topics are not Language-Dependant!

Practical Topics Theory TopicsAlgorithm

Topics

Coding StyleAnalysis of Complexity

Data Structures

DocumentationNumerical Storage &

ComputationRecursion

Testing & Debugging

Sorting

Assertions & Invariants

Searching

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Course Content, Cont.

• There is no single optimum way to navigate these topics.

• From example programs in class:– See examples (I hope!) of good coding style.– See examples of testing & debugging (I’m sure!).– Measure time of execution to verify complexity

analyses.– Test the effect of finite memory used to store numbers.– Code and demonstrate the data structures and

algorithms discussed.

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Course Content, Cont.

• Assignments will:– At first, be used to practice fundamental Java language

concepts.– Later, to explore concepts introduced in lecture.– And then to apply some of the algorithms learned to

practical situations.

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Course Content, Cont.

• To add to the excitement!…– Lectures will be shared with many examples

and class problems.– Your questions are very important!! They will

really help to make the lectures more interesting!

– Other kinds of class participation?…

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How to Pass

• Evaluation:– 25% Assignments (5% each?)– 25% Midterm– 50% Final Exam

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How to Pass – Cont.

• Do all the assignments and all practice questions yourself. Do not look at solutions until you have tried them.

• Ask if you have questions:– Ask me – during lecture, by E-mail, after lectures or in

the WebCT forum.– Ask TA’s in lab, by E-mail.

• Read lecture notes.• Get the textbook if you need more help.• Many other resources are listed on the web site.

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Warning!

• Most of the contents of a first year programming course like APSC142 or CISC101 will be crammed into the first three weeks.

• If you do not have any programming background nor a strong aptitude for coding, you might have problems keeping up!

• If you need more time with basic Java, pick up a first year-level textbook and/or see if you can spend more time with the TA’s.

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Today

• Demo’s of environments:– One time only use of JDK - just to show you what is

going on “under the hood”.– BlueJ– eclipse

• Note that you can use whatever development tool you wish. We officially only support eclipse. For assignments hand in your *.java files only.

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A Simple Java Program

public class HelloProg

{

public static void main (String [] args)

{

System.out.println ("Hello there!");

} // end main method

} // end HelloProg class

• The “//” denotes an in-line comment. Everything else on the line is ignored by the compiler.

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A Simple Java Program – Cont.

• The compiler ignores any “white space” in your source code – returns, line feeds, tabs, extra spaces and comments.

• Here’s our little program without white space (imagine this all on one line):

public class HelloProg{public static void main(String[] args){System.out.println("Hello there!");}}

• This does still run, but it is hard to read…

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Running a Java Program

• What happens when a program is run?• Remember that Java code is platform

independent.• Compilation of Java source code (HelloProg.java)

is done by a compiler (javac.exe) that creates a “byte code” file (HelloProg.class) that is still platform independent.

• This byte code file cannot be viewed or edited and is very compact.

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Running a Java Program – Cont.

• Each platform capable of running Java programs has its own “JVM” or Java Virtual Machine – also called a “byte code interpreter”.

• This program (java.exe on a Wintel machine) runs the byte code file to perform on a specific platform.

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Running an Applet

• Helps to explain why Java programs run this way:• An Applet is a small byte code file that is linked to

a web page.• Compact is important in order to minimize

download times.• The JVM is part of the browser, and browsers are

platform specific, but the applet is not.• In the case of an applet, the JVM built into the

browser runs the applet.

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A Simple Java Program – Cont.

• Back to our little program:

public class HelloProg

{

public static void main (String [] args)

{

System.out.println ("Hello there!");

} // end main method

} // end HelloProg class

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A Simple Java Program – Cont.

• A Class is an “Object” in Java. All Objects in Java are Classes…

• A Class is a container – it holds attributes (data) and methods (code that does something).

• Our class is called “HelloProg”. Our class must be defined in a file called “HelloProg.java”.

• The code “public class HelloProg” is used to declare the class.

• The contents of the class are contained in a set of curly brackets: “{ }”.

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A Simple Java Program – Cont.

• Our little class does not contain any attributes (data) and only has one method called “main”.

• The main method is declared using the code:

public static void main (String [] args)

• As before the code is contained within: “{ }”.

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The main Method

• For the JVM to run a program, it must know where to start.

• By design, the starting point is always the execution of the main method.

• The JVM expects the main method to be declared exactly as shown – the only thing you can change is the name of the String array, called “args” in this little program.

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A Simple Java Program – Cont.

• Our main method contains only one line of code:

System.out.println ("Hello there!");

• It prints out “Hello there!” to the screen (or “console”). We’ll talk more about I/O (“Input/Output”) later.

• Note the “;” at the end of the line of code. Since the Java compiler ignores white space, it must use these characters to determine when a line finishes.