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Documentation. Javadocs. Recall. Design/Documentation. An essential ingredient of good Object Oriented programming is known as design by contract. This means that before modules are written a specification or contract is written which states
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Documentation Javadocs
Recall Design/Documentation • An essential ingredient of good Object Oriented programming is known as design by contract. • This means that before modules are written a specification or contract is written which states • What preconditions must be met for the module to properly function • What is the purpose of the module • What will be the state of things after the module executes which is known as the postconditions
Recall Example • A module located in a Queue class which will dequeue the element at the head of the queue. • Precondition • The queue must be instantiated. It is recommended that isEmpty be run to assure that their is an element to dequeue • Purpose • Remove the element at the head of the queue and return it to the user. It will be an Object. • Postcondition • The queue will have one fewer element unless the queue was empty to start with in which case the method will return null and the queue will be unchanged
Design/Documentation • Java comes with an excellent documentation tool called Javadoc • Usage of the Javadoc system requires following several steps • First special Javadoc block comments are added to source files. • Javadoc block comments start with /** and end with */ this they function like regular comments • Each class, field and method should be commented with a Javadoc comment just before the actual item.
Javadoc • The comment should start with a short descriptive phrase followed by a period . • Then a longer description of the purpose of the item may be added. • HTML may be embedded • Special tags can be used such as @author @revision @parameter @return • The precondition and postcondition should be included.
Javadoc • Once commenting is complete the Javadoc program is run from the OS prompt. • If for example a group of class files for a given project are located in the same directory then Javadoc may be run by typing javadoc *.java • When the program runs it will report any problems and will produce a series of HTML files documenting all classes, methods and fields. • A Javadoc template is on the next slide followed by a sample
Javadoc Template /* -------------------------------------------------*/ /** Descriptive phrase. Longer statement of purpose. <BR><B>Precondition:</B> Precondition goes here <BR><B>Postcondition:</B> Postcondition goes here @param p1 A description of this parameter @param p2 A description of this parameter @ return A description of the return value */ public int someMethod(double p1, String p2) { return 0; } Note: The leading comment of “---” characters is not part of the Javadoc system but will make code easier to read