Class 04: An Introduction to Java (1)

Held: Wednesday, 31 August 2005

Summary: Today we begin our exploration of Java with some background and a laboratory experience.

Related Pages:

• EBoard.
• Lab: An Introduction to Java.

Assignments

• Reread An Introduction to Java, Java Packages, and Java in the MathLAN in Espresso.

Notes:

• Don't forget tomorrow's convo!

Overview:

• Java basics.
• Questions on the readings.
• Lab.

Some Basics of Java

• Java is a popular object-oriented language.
• What do you expect to see in an object-oriented language?
  • Support for defining classes: The templates that let us build objects.
  • Support for creating objects: The primary components of our programs.
  • Some how to "start" our program: Build the initial objects and tell them what to do.
  • Some forms of protection or encapsulation.
  • Inheritance: Ways to define new classes in terms of old classes.
  • Polymorphism: Ways to apply the same function to different classes.
• In Java,
  • Class Definition: Each class is usually defined in a separate file, typically NameOfClass.java.
    • Related classes are typically grouped into packages.
    • Classes contain a list of fields (along with what type of value they hold) and methods.
  • Object Creation: New objects are created by writing new, the name of the class, an open paren, any parameters the constructor for the class needs, and a close paren.
  • Starting: A special class (which I call the main class) contains a method called main which one uses to start the program.
  • Protection: Fields and methods may be prefixed by a protection level (private, protected, or public)
  • We'll visit inheritance and polymorphism later.

Your First Java Lab

• Begin the introductory Java lab.
• We will continue the lab in the next class.