Creating Classes part 4

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Creating Classespart 4

• Barb Ericson
• Georgia Institute of Technology
• Oct 2005

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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

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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

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Javadoc Comments

• Add a comment before the class definition
• That explains the purpose of this class
• And says who wrote it
• _at_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.
• _at_author Barb Ericson
• /
• public class Student

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Method Comments

• Add a comment before each method
• What the parameters are
• _at_param name info
• What is returned
• _at_return info
• /
• Method to set the name for this student
• _at_param theName the new name to use
• _at_return true if success else false
• /
• public boolean setName(String theName)

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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

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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

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Javadoc Exercise

• Add a class javadoc comment and method javadoc
  comments to the Student class
• Execute Javadoc and check out the created
  documentation

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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 teachers name
• The period number
• The students in that period

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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
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Creating a ClassPeriod class

• We want fields for the
• Teachers 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

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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 Student35

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Create a Class Exercise - Continued

• Add constructors to ClassPeriod
• Add the no argument constructor
• Add a constructor that takes the teachers name
  and the period number
• Remember that constructors are declared as
• public ClassName(paramList)

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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

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Override toString

• Add the following method to ClassPeriod
• public String toString()
• Add code to the method to return a String with
  the teachers name, the period number, and the
  number of students in the class period
• The length of the array isnt a count of the
  actual students
• Find out how many in the array are not null

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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