Transcript www.drjava.org

DrJava
A lightweight pedagogic environment for Java
Eric Allen, Robert Cartwright, and Brian Stoler
Rice University
{eallen,cork,bstoler}@rice.edu
http://drjava.sourceforge.net
DrJava is:
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A Java IDE
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Free
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Open source (GPL)
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An extreme programming project
Teaching Programming is Hard
Three complimentary concerns
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Concepts
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Syntax
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Tools
Editor/command prompt
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Learning curve
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Editing, compiling,
executing separated
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Frustrating!
Standard IDEs
(JBuilder, Forte/Netbeans, etc.)
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Learning curve (too many features!)
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Hide the language
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Cost/availibility
Solution: DrJava
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Simple and intuitive
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Leverages students' understanding of
language
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Don't hide the code, embrace it!
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Allow students to interactively evaluate
expressions and statements
Small (800k .jar file!)
Editor
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Transparent interface
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Consistent, automatic indenting
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Correct syntax highlighting
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Updated at keystroke granularity
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Automatic paren balancing
Integrated Compiler
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List of errors integrated with editor
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Compiler is a plugin
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javac 1.3
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javac 1.4
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JSR-14 prototype
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gjc
Interactions Pane
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Supports a read/eval/print loop
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No need for
public static void
main(String[] args)!
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Teaching static and arrays
can be postponed
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Convenient way to run
preliminary tests
Interactions Pane (cont.)
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Great for exploring the language
Applications
Introductory CS classes
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Great for inclass demos
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Upperlevel courses
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Distinctive features useful for all developers
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We use it in developing DrJava!
Future Directions
Integrated testing and debugging
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Seamless integration of JUnit
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Debugger
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Step into/out of/over methods
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Use interactions pane at breakpoints, in scope
Future Directions
Language levels  incremental presentation of syntax
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Tailor environment to support teaching
language constructs in stages (like in
DrScheme)
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Prevents generating bogus error messages,
e.g., accidental definition of inner clases
Implementation
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30,000 lines of Java code (Java 1.3 or 1.4)
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Incorporates DynamicJava (open source)
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Runs on any Java 1.3 or 1.4 VM
(Windows, MacOS X, Linux, Solaris)
A case study in XP
software development
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Pair programming
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Unit tests
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31% of code in tests
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Must pass all tests to commit code
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Incremental specification and
implementation
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Frequent releases (>1 daily)
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Program has advanced substantially since
we wrote the paper
A case study in XP
software development (cont.)
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Developed first generation system in three
months with 5 students
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Continuing development in a software
engineering class
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New students contributed within three weeks
Benefits of open source
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Everyone welcome to propose source code
changes (but they better have unit tests!)
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sourceforge.net helps manage open-source
projects
Download DrJava!
http://drjava.sf.net