Creating Classes part 4

1. Creating Classespart 4 Barb Ericson Georgia Institute of Technology Oct 2005 Georgia Institute of Technology

2. Learning Goals • Computing concepts • Comments • Why add comments? • Types of comments • How to add Javadoc comments • How to preview HTML from Javadoc comments • How to create HTML for all classes in a directory • Creating another class • Using UML to show classes and the relationships between them Georgia Institute of Technology

3. Comments • You should add comments to your code • To make it easier to read and change • Comments are ignored by the complier • Not added to the byte codes • Java has 3 kinds of comments • // comment ends at the end of this line • /* comment ends with next */ • /** Javadoc comment that ends with */ • can be used by the javadoc utility to create HTML documentation Georgia Institute of Technology

4. Javadoc Comments • Add a comment before the class definition • That explains the purpose of this class • And says who wrote it • @author Barb Ericson /** * Class that describes a student. A student has a * name and an array of grades. You can get * information about a student such as her/his * name and grade average. * * @author Barb Ericson */ public class Student Georgia Institute of Technology

5. Method Comments • Add a comment before each method • What the parameters are • @param name info • What is returned • @return info /** * Method to set the name for this student * @param theName the new name to use * @return true if success else false */ public boolean setName(String theName) Georgia Institute of Technology

6. Previewing Javadoc HTML • Click on Tools • Click on Preview Javadoc for Current Document • This will generate the HTML from the javadoc comments and display it • The HTML document will display Georgia Institute of Technology

7. Generating all HTML for Directory • In DrJava click on the Javadoc button • to create the HTML documentation • based on the Javadoc comments • This will generate HTML for all files in the same directory as all open files • Generates an index.html as a starting point Georgia Institute of Technology

8. Javadoc Exercise • Add a class javadoc comment and method javadoc comments to the Student class • Execute Javadoc and check out the created documentation Georgia Institute of Technology

9. Create a ClassPeriod • A teacher has students in each class period • Each period can have different students • For a class period we might want to know • The teacher’s name • The period number • The students in that period Georgia Institute of Technology

10. UML Class Diagram • There is a standard way to diagram object-oriented classes • It is a UML class diagram • It shows the classes as boxes and the relationships between them Shows inheritance Has a or association Georgia Institute of Technology

11. Creating a ClassPeriod class • We want fields for the • Teacher’s name • Period number • Students in the period • What type should each of these be? • A name can be a string • A period number can be an integer • The students in the period can be an array of Student objects • With a max of 35 students in a class period Georgia Institute of Technology

12. Create a Class Exercise • Declare a new class ClassPeriod in the file ClassPeriod.java • Add the fields: • private String teacherName; • private int periodNumber; • private Student[] studentArray = new Student[35]; Georgia Institute of Technology

13. Create a Class Exercise - Continued • Add constructors to ClassPeriod • Add the no argument constructor • Add a constructor that takes the teacher’s name and the period number • Remember that constructors are declared as public ClassName(paramList) { } Georgia Institute of Technology

14. Add Accessors and Modifiers • Add methods to get and set the fields in the class period public String getTeacherName() { return this.teacherName; } public void setTeacherName(String theName) { this.teacherName = theName; } Georgia Institute of Technology

15. Override toString • Add the following method to ClassPeriod public String toString() { } • Add code to the method to return a String with the teacher’s name, the period number, and the number of students in the class period • The length of the array isn’t a count of the actual students • Find out how many in the array are not null Georgia Institute of Technology

16. Summary • Comments are added to make a program • Easier to read and understand • Comments are ignored by the compiler • There are three types of comments in Java • // end of line • /* multi line */ • /** java doc */ • Javadoc is a utility that comes with the jdk • Produces HTML documentation from Javadoc comments • UML is a standard way to diagram object-oriented designs • A class diagram shows classes and the relationships between them Georgia Institute of Technology