3.1 Documentation & Java Language Elements

3.1.1 Purpose of documentation

• Assist the programmer with developing

the program

• Assist other programers who wish to use

or modify the program

3.1.2 Guidelines for documenting classes

• Block comments – Start with /* and end

with */. Can occupy multiple lines

• Single line comments – The line starts

with //

3.1.3 The javadoc parameters

• The javadoc program can create HTML documents from

the comments in the program’s source file

• To create javadoc comments,

use /** and */

• Special tags can be imbedded in the comments

@author, @version, @param, @return, etc

3.1.4 Java API documentation

3.1.5 Generating API docs for classes using the javadoc tool

3.2.2 Keywords

• Keywords form the Java

vocabulary

• The compiler is case-sensitive

3.2.3 Identifiers

• Labels assigned to data or storage

addresses

• Rules for identifiers:

– Any alphabetic character

– First character must be a letter

– Cannot contain space, % or #

– Cannot be keywords

3.2.4 Use of braces, semicolons, commas, and white space

• A block is a collection of statements

bounded by braces { }

• A statement consists of one or more lines

of code, followed by a semicolon ;

• Commas are used to delineate data

• Whitespace is used to separate

keywords and identifiers

3.3.1 Data storage introduction

• Registers – Memory in the CPU

• The Stack – Memory for methods and

local variables

• The Heap – Memory to store objects

• Static – Stores data that will not change

during the life of the program

• Constant – Values that never change.

3.4.1 Java language types

• Data type is the classification of forms of

information

• Data type is declared using keywords

• Java is stronglytyped

3.4.2 Java primitives

• boolean – true or false

• char – Stores a single UNICODE character

• byte – Signed whole numbers from -127 to +128

• short – Signed whole numbers from -32,768 to +32,767

• int - Signed whole numbers from -231 to 231 -1

• long – Signed whole numbers from -9x1018 to 9x1018 -1

• float – Decimal values up to 6 – 7 decimal places

• double – Decimal values up to 14 – 15 decimal places

3.4.3 Java references

• Objects are created in heap memory

• Programs use a variable that references

the object

• The program

acts on the

object by using

the reference

3.4.4 Data

• Object Data – Instance of a class, stored on the heap

• Static Class Data – Available before the object is created

• Local Data – Exists in methods, stored on the stack

• Constants – Data that will not change

• Variables – Holds a primitive or a reference to an object

3.4.4 Data (example)public class Student

{

private final String studentName;

public static final int courseNumber = 12345;

public String grade;

public Student(String name, String grd) {

studentName = name;

grade = grd;

}

public void changeGrade(String grd) {

grade = grd;

}

public String getName() {

return studentName;

}

}

Try to Identify!!!!!

1. Object Data/Variable

2. Static Data/Variable

3. Local Data/Variable

4. Constants

3.5.2 Elements

• Class – Template or blueprint for object

creation

• Method – A block of statements that control an object’s behavior

• Constructor – A special method that is

called when the object is created

• Modifiers – private, public, protected,

default, static, final

constructor

method

class

3.5.2 Elements

public class Student

{

private final String studentName;

public static final int courseNumber = 12345;

public String grade;

public Student(String name, String grd) {

studentName = name;

grade = grd;

}

public void changeGrade(String grd) {

grade = grd;

}

public String getName() {

return studentName;

}

}

3.6.1 Five steps of object creation

• Declaration of a reference variable

• Default initialization

• Explicit initialization

• Execution of the constructor

• Assignment of object’s address to

reference variable

3.6.3 Mutability, Garbage Collection & Finalizers

• Most data is mutable, and can be changed. To make it immutable, use the final keyword

• Garbage collection frees up memory occupied by unused objects. This process cannot be controlled

• Every object inherits a finalizer method, that will be executed when the object is released

Individual activity & Lab Work

• Possible Lab Schedule every: – Monday, 15.00-16.50 or

– Friday, 14.30 - 15.20 (PUSKOM-FTUI)

• TODO LIST (finished before next session):– Read through the online curriculum

– Take the module exam 1 – 3 (Start: Thursday)

– Do LABs:

• 3.1.6.1 Insert Documentation for Classes in the JBANK Application

• 3.1.6.2 Generate API Docs for JBANK Classes with the javadoc Tool

• 3.5.1 Define Variables

• 3.5.9 Apply Access Modifiers

• 3.6.1 Use of Constructors

• 3.8.1 Create the Classes for Phase I of the JBANK Application

Note: Red bold color is obligatory to be submitted to ECourse System!