Transcript chap3 - Website Staff UI

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 strongly
typed
3.4.2 Java primitives
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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
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;
}
constructor
class
public void changeGrade(String grd) {
grade = grd;
}
method
public String getName() {
return studentName;
}
}
3.6.1 Five steps of object creation
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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:
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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!