CS 211: Video Presentations

Ignore any due dates mentioned in the videos as they are relevant only to previous years.

The videos give a brief overview of inheritance. The PrintWriter class discussed in the 2nd video and an example of how to extend is the subject of the final video. These two are particularly relevant to Spring 2017 Lab 5 Exercises.

• Inheritance Basics
  • How to set up a couple related classes
  • Child inherits fields and methods from parent
• PrintWriter Intro
  • An output class
  • Can write to the screen
  • Can write to files
  • As Scanner is to input, PrintWriter is to output
• ScreamWriter extends PrintWriter
  • Inherit behavior like println from PrintWriter
  • But modify it subtly
  • Instead of printing, SCREAM THE TEXT
  • Utilize a method from String to upper case
  • Direct applications Lab05 Exercises
• Defining equals(Object) Methods
  • All classes have an equals(Object) method
  • Inherited version usually doesn't behave as expected
  • Overriding it for proper deep equality is customary
  • Requires instanceof checks and casting
• Dynamic Dispatch
  • Many versions of a method can exist
  • Invoking a method x.doSomething() calls the most special version of doSomething()
  • Version run depends on the runtime class of x
  • Calling a method on an argument doIt(x) does not call a special version
  • Whatever compile time type x is will be the version of the method called
• Project 5 Testing Problem Intro
  • Setup for Project 5 Testing problem
  • DrJava Testing, setting class path
  • Dealing with testing multiple implementations on command line and batch scripts
• Project 5 DrJava Debugger
  • Basic debugger setup
  • Stepping in/over/resume
  • Debugging with program command line arguments