Lecture 1

Next: Lecture 2

Lecture 1 Handouts

Course outline
Assignment 0
Doing your work in CSC108S

Announcements

The Faculty of Arts and Science wants me remind you that they have to have either a "registration card" or a U of T photo library card. To get an Arts and Science photo ID "registration card", students can come to Ramsay Wright room 429 either during the regular hours (MW 9-12, R 2-5) or during special evening hours:

5-7 p.m. on May 19, May 20, or July 14.

Because of overcrowding, in fairness to enrolled students, auditing is discouraged.

IF THE COURSE IS FULL AT THE END OF THE FIRST WEEK OF CLASSES, NO LATER ENROLMENTS WILL BE PERMITTED. That's a Faculty rule.

Readings

On the course Web page read:

General advice on assignments
Program and debugging advice
How to print ``Print Java Assignment''.

In the text read

Chapters 1 and 2
motivation for encapsulation p 145
Read Guide to VisualAge

Handouts

Course outline
Assignment 0
Doing your work in CSC108S

Humans versus Computers

computers are quicker at logic, sequence, selection and iteration but can't easily be made to shift context.
people are better at establishing and changing context but attention sometimes wavers and logic is faulty.

People naturally think in an object oriented way.
People have a working memory limit of 7+-2 objects.

Black box
class versus object
syntax versus semantics
algorithm versus program

Why use Java?

Java (capital J) is a high-level, third generation PL, like C, Fortran, Smalltalk, Perl etc.
special about Java - it lets you write programs called applets that can be downloaded from the Internet and played safely within a web browser.
Java is a platform for application development. A platform is a loosely defined computer industry buzzword that typically means some combination of hardware and system software that will mostly run all the same software.

What is Java?

The javac compiler, the java interpreter, the Java programming language, and more are collectively referred to as Java.
Java was designed to make it much easier to write bug free code.
object oriented programming

data is represented by objects
Objects have two sections, fields (instance variables) and methods.
Fields tell you what an object is.
Methods tell you what an object does or can be done to it.

object oriented programming

These fields and methods are closely tied to the object's real world characteristics and behavior.
When a program is run messages are passed back and forth between objects.
When an object receives a message it responds accordingly as defined by its methods.

Why Object Oriented?

Object oriented programming has a number of advantages

Simpler, easier to read programs
More efficient reuse of code
More robust, shorter, error-free code

Consider this java program

class HelloWorld {
 
  public static void main (String[] args) {

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

  }

}

There are three steps to create a Java program:

In a command line environment (Unix or Dos) do this

# Step Comment

1 writing the code Use an editor on HelloWorld.java. The file name must match the class name, HelloWorld.

2 compiling the code javac HelloWorld.java

3 running the code java HelloWorld

#	Step	Comment
1	writing the code	Use an editor on HelloWorld.java. The file name must match the class name, HelloWorld.
2	compiling the code	javac HelloWorld.java
3	running the code	java HelloWorld

Computer Session at the PC site.

Login : h108xxxx
Passwd : Student number
run Visual Age for Java - double click
goto Workbench
create a new project - dialog box
type in class with main method
click on FILE & SAVE
click on Run Button
create data file - in scrapbook editor
FILE/export - programs to H: drive !!!
FILE/quit
Logout

Comments are to make code easier for people to understand Comments are ignored by the computer:

/* use this anywhere
even splitting comments
over multiple lines */
// use this for end of line comments only

// This is the Hello World program in Java
class HelloWorld {

  public static void main (String[] args) {

    /* Now let's print the line Hello World */
    System.out.println("Hello World!");

  } // main ends here

} // HelloWorld ends here

What is a class? Fields say what an object is
Methods say what an object does

class Point {

  double x;
  double y;
}

What is an object? Create objects with the new keyword followed by a constructor:
Point origin = new Point();
origin.x = 0.0;
origin.y = 0.0;
System.out.println("The origin is at (" +
origin.x + ", " + origin.y +")");

Lecture 2.

Next: Lecture 2.

Craig MacDonald

Fri May 15 16:09:12 EDT 1998