Class 05: Lab: Objects and Methods, Continued

Held Monday, January 31, 2000

Overview

Today, we continue our investigation of Java basics with further work on Lab J2.

Notes

• When a link doesn't work on the course Web, please drop me a link. Some are generated automatically, and the program that generates them doesn't always work correctly.
• The exotic programming languages study group has just started. This semester, they're studying, Python, a ``hot'' Web language. Talk to Mr. Stone about details.
• Don't forget today's CS brown bag lunch.
  • I won't be there because I need to prepare my afternoon classes.
• I've made minor changes to the syllabus for this week.
• I managed to injure my foot over the weekend, and should be hobbling around for the rest of the week.
  • I may be behind in class prep.
• Assigned:
  • Read Lab J3
  • HW1 is still due tomorrow.

Contents

• Classes, Revisited
• Lab J2 Continued
• Reflections

Summary

• The usss of classes, revisited
• Lab J2, continued
• Initial reflections on Lab J2

Classes, Revisited

• I've mislead you slightly about classes, and that's because the design of Java is not as wonderful as it could be.
• Ideally, classes serve as platonic ideals: they are the templates we use when we build objects.
• However, classes also have a second use: We also use classes to hold main methods.
  • The method has to go somewhere, and since classes naturally hold methods, a class is a reasonable place to put them.
• You will typically build three kinds of classes:
  • Utility classes: These have no main method. They support other classes. You never directly interpret these classes.
  • Main classes: These have only a main method and provide the script for the program. You typically start with these classes.
  • Hybrid classes: These not only serve as a template, but also contain a main method. We use these as a kind of shorthand when we need both kinds of classes.

Lab J2 Continued

Continue working on Lab J2. You'll need to finish it tonight. Do not do the optional applet section.

Reflections

What have you learned about Java so far?