1 CMSC 131 Fall 2009 Jan Plane (adapted from Bonnie Dorr) Lecture Set #13: Args Array and Commenting Review 1. Arguments to Main Method 2. Commenting Review CMSC 131 Fall 2009 Jan Plane (adapted from Bonnie Dorr) 1 Arguments to main Recall prototype of main method public static void main (String[] args); args is array of Strings args come from operating system When user runs executable … … s/he can provide arguments Demonstrations of Using the Args array CMSC 131 Fall 2009 Jan Plane (adapted from Bonnie Dorr) 2 Types of Documentation Two kinds of code commentary in Java Implementation comments Interface comments JavaDoc from inside Eclipse from outside of Eclipse Common Errors in Commenting Too many comments: This can obscure the flow of your program. Too few comments: Your intent may not be understood (code is never “self-documenting”!) Comments that repeat the code: int total = 0; // initialize integer total to 0 Using comments to conceal unclear code: …just rewrite the code double a = h*w; // set the area (a) to the height (h) // times width (w) double area = height * width; Uninformative comments: “What the heck does that mean?” double d = processValue( ); // Change later (legacy) Misleading / erroneous comment: These are dangerous for ( int i = 0; i < a.length-1; i++) // run through the //whole array2 CMSC 131 Fall 2009 Jan Plane (adapted from Bonnie Dorr) 3 Javadoc Documentation Class comments: Immediately prior to each public class, add a javadoc comment that explains what the class does. You can also add the following special “tags”, which javadoc recognizes and provides special formatting for: @author – the author of the class @version – the current software version number @see – refer the reader to related classes Example: In Rational.java /** * This class implements a rational number object, * and provides methods for performing arithmetic * on rational numbers. * @see java.lang.Math * @author Schultzie von Wienerschnitzel III * @version 3.14159 */ public class Rational { … } Sample javadoc class comment CMSC 131 Fall 2009 Jan Plane (adapted from Bonnie Dorr) 4 Javadoc Documentation Method comments: Immediately prior to each public method, add a javadoc comment explaining what the method does, the meanings of the parameters, the return value, and any errors. The following tags are recognized: @param – give the name and description of each parameter. There should be one for each parameter. @return – describe the return value (unless it is void) @throws – (exceptions that could propagate out from this method) @deprecated – (Usually for system use: indicates that a method should be avoided, since better alternatives exist) Example: /** * Multiplies two rational numbers and returns their the product. * @param q The first operand. * @param r The second operand. * @return A reference to a newly created Rational with the sum. */ public static Rational multiply( Rational q, Rational r) { …
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