Appendix C
Glossary
- abstract class
- A class that is not instantiated directly. Abstract classes exist so that subclasses
can inherit variables and methods from them.
access control- A way to restrict access to a class's variables and methods. The modifiers public,
private, protected, and private protected, placed before a variable name or function
declaration, specify the kind of access granted.
action- An applet method that can be defined to identify the kind of event that has occurred
and act on that event.
Alignment- Identifies how a particular object will line up relative to other objects in
a container.
API- Application Programming Interface. The Java API contains classes a developer
can use to build applications and applets. Currently, the Java API provides classes
to support the language itself, I/O capability, network capability, user interfaces,
applets, image management, interaction with a platform-specific toolkit, and general
utilities.
- applet
- A Java program that runs in the context of a Java-capable browser or the AppletViewer.
Java applets extend the content of Web pages beyond just graphics and text.
- AppletViewer
- A tool created by SUN to run applets without a browser.
- array
- An indexed set of data where each data item is of the same type. An element of
an array is referenced by its index.
- attribute
- A specifier for an HTML tag (for example, code is an attribute of the <APPLET>
tag).
- attributes
- An object's variables, or state information.
- AWT
- The Abstract Windowing Toolkit, or group of classes for writing programs with
graphical user interfaces. The AWT contains classes for Components (for example:
Button, TextField, Canvas, Choice, List, TextArea, Checkbox, List, MenuItem, Scrollbar,
and Label), classes for Containers (for example: Window, Frame, Panel, Dialog, and
FileDialog), and classes to help with layout, graphics, and images.
- behavior
- Describes the way a class reacts to events in the environment, messages, and
changes to variables. Behavior depends on the state of an object. A class maintains
state information in its variables and reacts to its environment through its methods.
- browser
- A program used for reading, displaying, and interacting with objects on the World
Wide Web.
- bytecode
- The machine-independent output of the Java compiler and input to the Java interpreter.
- cast
- To coerce an object of one data type to another type.
- class
- A collection of variables and methods that an object can have, or a template
for building objects.
- .class file
- A file containing machine-independent Java bytecodes. The Java compiler generates
.class files for the Java interpreter to read.
- CLASSPATH
- An environment variable used to define all the directories where .class files
can be found.
- class variable
- A variable allocated once per class. Class variables have global class scope
and belong to the entire class instead of an instance.
- code
- An attribute of the HTML <APPLET> tag that specifies the class
to load. The term "code" also refers to source code, which is the syntactical
representation of a program.
- codebase
- An attribute of the HTML <APPLET> tag that specifies the location
of the classes to load.
- Common Object Request Broker Architecture
- A standard for distributed objects being developed by the Object Management Group.
- compiler
- A language translator. A program that transforms source code into another format
without executing the program.
- conditionals
- Programming constructs that support branching or execution of different statements
when different conditions are true. Java conditionals are case statements,
if statements, and the ? (conditional) operator.
- constructor
- A method that is used to create an instantiation of a class.
- Container
- An object which holds several objects. Usually used with java.awt.container,
which contains several java.awt objects. The most common container object is java.awt.panel.
- content handler
- A Java routine used to process a particular MIME type (for example, text/html).
- CORBA
- See Common Object Request Broker Architecture.
- deprecated
- A comment code that was added to Java to allow programmers to see quickly and
unambiguously that a particular portion of the API is no longer utilized and has
been superseded by some other mechanism.
- destroy()
- An applet method used to do final cleanup before an applet unloads. Applets override
this method when resources need to be released that are not released by the stop()
method.
- double buffering
- A technique used to reduce flicker in animations. The image or drawing is painted
into a temporary space. Then the finished object is drawn to the screen all at once.
- DTD
- Abbreviation for Document Type Definition. A DTD file formally describes a particular
markup language, such as HTML.
- encapsulation
- A way to contain data and methods in a class so that its methods and variables
may be added, changed, or deleted without requiring the code that uses the class
to change. This object-oriented programming technique makes a class look like a black
box to the outside world.
- event handling
- Identifying events (for example, mouse clicks and button presses) and reacting
to them. Events can be handled with the action method, a method corresponding
to the event (for example, MouseDown), or the handleEvent method.
- exception
- A signal that something has happened to stop normal execution of a program, usually
an error.
- exception handler
- Code that responds to and attempts to recover from an exception.
- expression
- Mathematical, comparative, and other kinds of operations that can be evaluated
to a single value. For example, 1+3+9*7+Math.pow(45,3.3) is an expression.
- extends
- A keyword used to make one class a subclass of another; for example, class subclass
extends superclass.
- final
- A modifier that prevents subclass definition, makes variables constant, and prevents
a subclass from overriding a method.
- finalize
- A method that is called when there are no further references to an object and
it is no longer needed. This method releases resources and does any other necessary
cleanup that Java does not handle during garbage collection.
- Gamelan
- A registration site on the Web for Java applets and applications. Items registered
here often contain the Java source.
- garbage collection thread
- A Java thread that automatically frees memory no longer needed by objects.
- GUI
- Graphical User Interface. A graphical user interface provides a friendly way
for a person to interact with a program. The user interacts with pictures and drawings
rather than just text. In Java, the AWT provides classes to support user interface
construction.
- Hashcode
- a number that can be used to uniquely identify an object. Usually used with a
hashtable.
- HotJava
- A Java-capable browser from Javasoft.
- hspace
- An attribute of the HTML <APPLET> tag that specifies the amount
of horizontal space (to the left and right) between the applet and the text on the
page.
- HTML
- Hypertext Markup Language, the language used to create Web pages.
- inheritance
- A property of object-oriented languages where a class assumes the methods and
variables of more general classes. A subclass automatically contains all of the methods
and variables that its superclasses contain. Note that access modifiers, such as
private, can place restrictions on the use of inherited items in Java.
- init()
- An applet method used to do one-time initialization before an applet begins executing.
- Inner classes
- Classes which are defined within the body of other classes, methods, or blocks.
The scope of these classes is limited to the body they are contained within.
- instance
- A concrete representation of a class or object. A class can have many instances.
- instance variable
- A variable allocated once per instance of a class.
- instantiate
- To create a concrete object from a class "template." New objects are
instantiated with new.
- interface
- A collection of methods and variables that other classes may implement. A class
that implements an interface provides implementations for all of the methods in the
interface.
- Internationalization
- The ability to utilize international codes, times, and other geographic data
within Java.
- interpreter
- A program that performs both language translation and program execution. java
is the Java interpreter.
- JAR
- See Java Archive Resource.
- java
- The program used to invoke the Java interpreter, which executes Java programs.
- Java
- An object-oriented language that can be used to create machine-independent applications
and applets.
- .java file
- A file containing Java source code.
- java.applet
- Java package that supports applet development. This package provides the ability
for an applet to get information about its context, communicate with other applets,
load images, and play sounds.
- java.awt
- Java package that supports the development of user interfaces.
- java.awt.image
- Java package that supports image processing.
- java.awt.peer
- Java package that links Java user interface code with a platform-dependent toolkit
like Motif or Windows.
- java.io
- Java package that supports reading and writing of files, strings, sockets, and
so on.
- java.lang
- Java package that supports the basic features of the language. This class does
not have to be explicitly imported into Java programs; it is imported automatically.
- java.net
- Java package that supports network connections.
- java.util
- Java package that provides useful utility classes like random number generation
and growable arrays.
- Java Archive Resource
- A method to package up class and data files into a single resource file. Can
greatly improve download time of applications and applets. Usually written as JAR.
- Java beans
- A specification which extends Java's "write once--run everywhere" capability
to reusable component development. Similar in nature to CORBA.
- Java Database Connectivity
- A database access API from JavaSoft that allows developers to access databases
with Java programs.
- javac
- A command for running the Java compiler.
- javac_g
- A command for running a non-optimized version of the Java compiler. The javac_g
command can be used with debuggers, such as jdb.
- Java-capable browser
- A Web browser that can run Java applets. Also called a Java-enabled or Java-enhanced
browser.
- javadoc
- A command that is used to generate API-style HTML documentation automatically.
- javah
- A command that can create C include files and stubs from a Java .class file.
The resulting C files allow C code to access parameters passed from Java, return
values to Java, and access Java class variables.
- javah_g
- A command that can create C include files and stubs with debug information from
a Java .class file.
- Javakey
- A tool included with the JDK that manages objects, including their keys, certificates,
and the trust associated with them.
- javap
- A command that disassembles Java .class files.
- JavaScript
- A Java-based scripting language.
- Java-SIG
- The Sun User Group's Special Interest Group for Java.
- jdb
- The Java debugger.
- JDBC
- See Java Database Connectivity.
- JDK
- The Java Developers Kit.
- literals
- umbers or character values. `x', `2', and `1.22' are all literals.
- loops
- Programming constructs that support repetitive execution of one or more statements.
Java has while, do-while, and for loops.
- main()
- The entry point into a Java application.
- method
- A routine that belongs to a class.
- method prototype
- The format of a method that specifies the name of the method, the return type,
and the parameter list. A method prototype is also called a signature.
- MIME
- Abbreviation for Multipurpose Internet Mail Extensions. The MIME specification
supports electronic mailing of many kinds of messages (for example, audio files,
images, and HTML).
- modifier
- A Java keyword that is applied to a method or variable declaration to control
access, control execution, or provide additional information. The keywords private,
public, protected, final, native, synchronized, and volatile are Java modifiers.
- multiple inheritance
- The ability for a class to inherit from multiple classes. Java does not support
multiple inheritance.
- multithreaded
- Having multiple threads of execution so that parts of a program can execute concurrently.
- native methods
- Methods that are declared in Java with the keyword native but are implemented
in another language. Usually, native methods are written to do something that the
Java API does not already do, to interact with a particular computer's hardware or
operating system or to improve performance. Since native methods are not portable
across platforms, applets cannot contain native methods.
- new
- The Java operator that is used to create a new instance of a class; for example,
MyClass c = new MyClass().
- object
- An instantiation of a class.
- object serialization
- A method of packaging the entire contents of an object in byte format. Can be
used to pass an object down any stream.
- OOP
- Object-Oriented Programming is the ultimate extension of the concept of modular
programming.
- override
- To replace a method inherited from a superclass. For example, applets frequently
override the init(), start(), stop(), destroy(),
and paint() methods inherited from the applet class.
- package
- A Java keyword used to assign the contents of a file to a package. Packages are
Java's mechanism for grouping classes. Packages simplify reuse, and they are very
useful for large projects.
- pointers
- Variables that contain machine addresses of data instead of the data itself.
The Java language does not support pointers.
- private
- An access control modifier that limits access to within the class itself.
- private protected
- An access control modifier that limits access to a class and its superclasses.
- protected
- An access control modifier that limits access to a class, the package, and its
subclasses. A subclass, however, cannot access a superclass's protected variables.
- protocol handler
- A Java routine that interprets a protocol, generally for a browser.
- public
- An access control modifier that allows access to a variable or method from anywhere.
- Reflection
- A new feature with Java 1.1 that allows objects to be inspected to reveal their
methods, constructors, variables, and other information.
- Remote Method Invocation
- A system which allows object instances to reside and process on multiple machines
transparent to the code.
- RMI
- See Remote Method Invocation.
- RMI Registry
- A tool included with the JDK--the Remote Object Registry. Creates and starts
a remote object registry on the specified port of the current host. Required before
a remote object can be started on a server.
- RMIC
- A tool included with the JDK--the Java RMI Stub Converter. Generates objects
from the names of compiled Java classes that contain remote object implementations.
- Runnable interface
- An interface that allows a class the ability to run in a distinct thread without
being a subclass of Thread.
- scope
- Defines where a method or variable is visible. A variable defined in a method
is visible only within the method; it has local scope. A variable or method defined
within a class is visible inside the class; it has class scope.
- ServerSocket
- A Java class that supports network connections for server objects.
- SGML
- Standard Generalized Markup Language, the grandfather of HTML.
- signature
- The format of a method. A signature specifies the name of the method, the return
type, and the parameter list. Also called a method prototype.
- Signed applet
- An applet that has been digitally signed to prevent tampering. See Javakey.
- Socket
- A Java class that supports the creation of network connections.
- start()
- An applet method used to begin execution and resume execution after an applet
has been temporarily stopped. Applets override this method, when they need to do
processing after a one-time initialization, and anticipate stopping temporarily (for
example, when the user leaves the applet's page) and restarting.
- statement
- A Java construct that controls program flow, controls execution of critical sections
of code, makes an assignment, imports a package, or declares membership in a package.
- static
- A Java keyword used to indicate that a variable is a class variable, allocated
once per class (for example, static int myinteger). When class variables change,
they change for every instance of a class.
- stop()
- An applet method that is overridden to stop execution (for example, stop sounds
when the user leaves the applet's page). Usually, stop() and start()
are implemented together, so stop() should be implemented in a way that
permits the start() method to resume execution.
- streams
- Controlled flows of data from one source to another. Java supplies several classes
to create and manage streams. Classes that handle input data are derived from class
InputStream, and classes that handle output data are derived from class
OutputStream.
- string
- A sequence of characters enclosed in double quotes in the generic sense. In Java,
strings are instances of the String class. Even the statement String mystring
= "This is my string."creates a String object.
- stub
- Part of the interface between Java code and a native method. A stub allows a
native method to access Java parameters, access Java class variables, and return
data to Java.
- subclass
- A class that inherits methods and variables from another class. The statement
class SubClass extends SuperClass means that SubClass is a subclass
of SuperClass.
- super
- A reserved word that refers to a class's immediate superclass.
- super()
- Shorthand for the superclass's constructor method.
- superclass
- A generalization of another class. X is a superclass of Y if Y inherits variables
and methods from X.
- synchronized
- A Java keyword that prevents more than one thread from executing inside a method
at once.
- this
- A reserved word that refers to the current class.
- token
- The smallest unit in a language that a compiler can recognize.
- type
- A specific kind of data in a program or programming language. In the Java statement
int my_integer = 1;, the int keyword indicates that my_integer
is an integer instead of some other data type.
- virtual machine
- An abstract, logical model of a computer used to execute Java bytecodes. A Java
virtual machine has an instruction set, registers, a stack, a heap, and a method
area.
- VRML
- Virtual Reality Modeling Language.
- vspace
- An attribute of the HTML <APPLET> tag that specifies the amount
of vertical space above and below the applet and the text on the page.