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JavaDoc and Contracts. Spring 2013. Documenting Contracts with JavaDoc. Contract model for methods Preconditions Postconditions JavaDoc Industry standard for documenting APIs Covers a lot more than contracts How to go from one to the other?. JavaDoc.
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JavaDoc and Contracts Spring 2013
Documenting Contracts with JavaDoc • Contract model for methods • Preconditions • Postconditions • JavaDoc • Industry standard for documenting APIs • Covers a lot more than contracts • How to go from one to the other?
JavaDoc • Javadoc is a tool that generates java code documentation. • Input: Java source files (.java) • Individual source files • Root directory of the source files • Output: HTML files documenting specification of java code • One file for each class defined • Package and overview files
Goal of an API specification • Knowledge needed for “clean-room” implementation. • Not a programming guide • Also a useful document, but very different • Defines “contract” between callers and implementations • Should be implementation *independent* • Exceptions are highly undesirable • But are sometimes necessary • Should contain assertions sufficient to test
Adding specification • Specifications are defined in comment lines. • /** *This is the typical format of a *simpledocumentation comment that *spansthree lines. */ • Inside the comment block, use <p> tags to separate paragraphs and javadoc pre-defined tags to define specific elements.
Placement of comments • All comments are placed immediately before class, interface, constructor, method, or field declarations. Other stuff between them is not permitted. /** *This is the class comment for the class *Whatever. */ import com.sun; // problem! public class Whatever {}
Structure of the specification Main Description Tag Section Postconditions? Preconditions?
Comments are written in HTML /** * This is a <b>doc</b> comment. * @see java.lang.Object */ Note that tag names are case-sensitive. @See is an incorrect usage - @see is correct.
Block tags and in-line tags • Block tags - Can be placed only in the tag section that follows the main description. Block tags are of the form: @tag. • Inline tags - Can be placed anywhere in the main description or in the comments for block tags. Inline tags are denoted by curly braces: {@tag}. /** * @deprecated As of JDK 1.1, replaced * by {@link #setBounds(int,int,int,int)} */
Overview Tags • @see • @since • @author • @version • {@link} • {@linkplain} • {@docRoot}
Package Tags • @see • @since • @author • @version • {@link} • {@linkplain} • {@docRoot}
Class/Interface Tags • @see • @since • @deprecated • @author • @version • {@link} • {@linkplain} • {@docRoot}
Field Tags • @see • @since • @deprecated • {@link} • {@linkplain} • {@docRoot} • {@value}
Method/Constructor Tags • @see • @since • @deprecated • @param • @return • @throws / @exception • {@link} • {@linkplain} • {@inheritDoc} • {@docRoot}
JavaDoc Style Hints from Sun • Use <code></code> for keywords and names • Use inline links economically • Omit parenthesis for methods and constructors • Example add vs add(index, value) • Phrases instead of sentences ok • 3rd person preferred to 2nd • gets the label vs. get the label • Begin method descriptions with a verb phrase • Gets the label… vs. This method gets the label… • Use “this” instead of “the” to refer to the object • Add description beyond API name
Javadoc in Eclipse In Eclipse, to create Javadocs: • Go to: File -> Export -> … -> Javadocs • Make sure the Javadoc command refers to the Javadoc command line tool • For example: C:\Sun\SDK\jdk\bin\javadoc.exe • Select the types that you want to create Javadoc for • Choosethe Use Standard Doclet radio button, and Browse for a destination folder • Click Next for more options, enter custom tags in the options text field
Directly supporting contracts • A variety of tools support design by contract explicitly by extending Javadoc • Example: JML (Java Modeling Language) • @pre • @post • @inv • Various tools at JML Home Page
Resources • Javadoc tutorial: • http://bazaar.sis.pitt.edu/jdtutorial/index.html • Eclipse Javadoc configuration tutorial: • http://open.ncsu.edu/se/tutorials/javadoc/index.html • How to Write Doc Comments for the Javadoc Tool • http://java.sun.com/j2se/javadoc/writingdoccomments/index.html • http://java.sun.com/j2se/1.4.2/docs/tooldocs/windows/javadoc.html • http://www.ibm.com/developerworks/java/library/j-jtp0821.html