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A B C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
A
ADT (Abstract Data Type)
- An abstract data type describes a set of data and what operations
can be performed on that data, but not how it is actually implemented in
a programming language.
API (Application Programming Interface) - The documentation of
the basic Java classes provided by Sun.
Applet - A Java application that runs on a Web page.
Application - A compiled piece of Java source code. Generally
the program that can be "run" through the Java interpreter.
Array - A collection of Objects of the same type.
ASCII - American Standard Code
for Information
Interchange, pronounced AS-KEY. It was designed
to be the standard international code for computer data, consisting of
128 characters (letters, numbers, punctuation marks and special symbols)
that have agreed decimal, hexadecimal and binary number values that all
computers will accept. See ASCII Table
AWT (Abstract Window Toolkit) - The Abstract Windows toolkit
provides the Objects and methods required to write GUI's in Java.
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B
Base - see superclass
Bit - The smallest element of a computer's memory. A "bit" can
either be on or off.
Byte - The smallest data type. It is eight bits in size meaning
it can take up a maximum of 2^8 (256) different values.
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C
Child - see subclass
Class - A blueprint for an Object. A class describes the variables,
constants and methods a particular instance will have.
Constructor - When an instance of a class is created, the relevant
constructor for the class will be executed. The name of the constructor
must be the same as the name of the class to which it belongs.
continue - In a loop, the continue instruction sends execution directly
onto the next iteration of the loop.
CORBA (Common Object Request Broker Architecture) - A language-independent
system that allows distributed objects to interact without regard to their
location or operating environment.
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D
Data Structure - The method of storing data. For example,
in a linear data structure like an array the data is stored in a contiguous
stream. Other data structures include linked lists and trees.
Data type - A data type describes a particular programming element
for storing data and the operations which can be performed on it. For example,
an basic int is defined by the values it can take and by operations such
as the arithmetic operations. When we describe the operations we can perform
on a data type but not how to implement them, we call the data type an
abstract
data type.
Derived - see subclass
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E
Encapsulation - The grouping together of related data
and functions inside a class definition.
Exception - An error. A programmer can prepare for a
certain Exception to be thrown if a particular error occurs.
extends - A Java keyword entered in the class definition line.
A class may extend only one other class as Java only supports single inheritance.
The class being extended is called the super class, the class doing the
extending is called the sub-class. The sub-class has access to the (public)
methods and (public) variables of of the super class through inheritance.
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F
Functional Design - An alternative approach to software
design as opposed to object oriented programming. In functional programming
each function applies some transformations to the data before passing it
on to other functions.
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G
Garbage Collection - In Java, if an object has no references to it,
it will be automatically deleted by the garbage collector.
GUI (Graphical User Interface) - A GUI normally consists
of one or more "windows" (referred to as "frames" in Java) which contain
text, pictures, buttons etc. Nearly all modern applications of any great
size provide a GUI for communication with the user as against a text based
front end like DOS prompts. Interaction with GUI's takes the form of mouse
clicks, and any textual information required is entered into text boxes
on the screen. The Java AWT takes care of GUI design, so a graphical front
end written in Java will work on all platforms.
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H
HTML (Hypertext Mark-up Language) - The language of
Web pages. Every web page is an HTML document. For all intents, HTML is
just a plain text document with special formatting flags typed in, which
tell the HTML viewer how the text should look.
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I
implements - A keyword in a class definition line which
is followed by a list of Interfaces. This infers that the class will provide
code for the methods in the Interface being implemented.
Inheritance - When a class extends another it inherits all the
(public) methods and (public) variables available to the previous class.
See Inheritance Diagram
Interface - Interfaces in Java are like abstract classes - they
define a set of methods and constants which will be provided, but don't
provide the code for the methods or any attributes the class will have.
It is up to the programmer who implements an interface in his class to
provide the actual code for the methods and the required attributes.
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J
JAR (Java Archive) - JAR is an archiving tool based
on zip. It is used to store many files (Java class files, images, sounds
etc.) into one compressed file for faster download. Entries in the archive
can be digitally signed by the author to confirm their origin.
JDBC (Java Database Connectivity) - JDBC is a Java API for executing
SQL statements (JDBC is not actually an acronym but a trademarked name,
but is generally taken to stand for "Java Database Connectivity"). See
JDBC
Home Page.
JECF (Java Electronic Commerce Framework) - The Java framework that
enables secure online transactions to be made - for example, an online credit
card system.
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K
Keywords - A keyword is, generally, an instruction to
the Java interpreter giving information about a function or control structure.
Keywords cannot be used as function names, class names, variables or constants.
Examples of keywords are "implements", "do", and "public". See Keyword
List
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L
Loop - A section of code that is repeated.
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M
Member - a variable or constant inside a class is said
to be a member of that class.
Member function - see Method
Method - A function defined inside a class
is said to be a member function or method of that class.
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N
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O
Obfuscation - Where you intentionally make your code misleaqding and
unreadable without directly encrypting it, to prevent people from hacking it.
Object - An instance of a class. Objects generally have
properties which can only be manipulated by the Object's member functions.
Object Oriented Programming - Generally, programming in a way
that implements encapsulation, inheritance, and polymorphism.
Overriding - When an inherited method is redefined in a sub-class
the inherited method is said to be overridden. If the method is called
from the super class, the original method is used, but if it is called
from the sub-class, the overridden method is instead called.
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P
Parent - see superclass
Polymorphism - A number of different classes of objects will
respond to the same request. Generally, wherever an instance of a class
is expected, an instance of its subclass can be provided instead because
all the methods and attributes of a class will have been inherited by its
subclass.
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Q
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R
Recursion - Where a function continually calls itself,
generally with less data to process in each successive call.
RMI (Remote Method Invocation) - RMI provides a method for
one Java object to invoke a method in another Java object across a network.
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S
Scope - The range over which something is visible is
known as its scope.
Single Inheritance - Where a class only inherits methods and
variables directly from one other class - the super class, as against inheriting
from many classes. See Inheritance Diagram
SQL (Structured Query Language) - SQL is a standard language for
accessing relational databases.
subclass - When a class is extended (through
inheritance), the new class formed is known as the subclass (or sometimes
the child or derived class). See Inheritance
diagram
superclass - When a class is extended
(through inheritance), the class that is being extended is known as the
superclass (or sometimes the parent or base class). See
Inheritance diagram
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T
this - Inside a class, "this" points to the current
Object instance - used to denote where a function should alter this
instance
of the class.
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U
Unicode - The character set used internally by Java.
Unicode characters take up two bytes of storage so can store 2^16 (65536)
different characters. Most conversions between ASCII and Unicode are done
by Java behind the scenes. See ASCII
URL (Universal Resource Locator) - The address of a particular
document on the Web. Every file on the Web (image, HTML document, zip file
etc.) has a unique URL.
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V
Variable - A named area of memory in the computer that
stores a particular value (integer, string, float etc.) at a certain time.
Visibility - If a variable or method is defined as "public" it
can be accessed by any other method anywhere. Visibility is the term used
to describe where object data and methods can be accessed from. It is left
to the programmer of the class to decide where these things will be visible.
void - a keyword in a function definition line which indicates
the function doesn't return a value.
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W
Wrapper Classes - In Java, wrapper classes are the object
oriented versions of the basic types. So the basic type "int" has the wrapper
class "Integer", and char has the wrapper class Character. Generally, a
basic type can be told apart from its wrapper class because the wrapper
class will be capitalised by convention as its a class.
| Basic Type |
Wrapper Class |
| boolean |
Boolean |
| byte |
Byte |
| char |
Character |
| double |
Double |
| float |
Float |
| int |
Integer |
| long |
Long |
| short |
Short |
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X
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Y
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Z
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