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APPENDIX D : Glossary

absolute positioning

In terms of the laying out of components, absolute positioning refers to the ability to specify the location of a component within its container without allowing the component to be resized or to move relative to anything else when the container is resized.

AWT

The set of portable Java components which were designed to look and feel like the native toolkit.

CLASSPATH

An environment variable which is used by the Java virtual machine to locate classes referred to in an application. CLASSPATH can contain directories or JAR files.

class structure

In Visaj, this is the tree on the right of the Class Editor window which shows the contents, order and signature of the Class under construction.

click over

To press and release the mouse button when the mouse pointer is above something.

code expression

In Visaj Property Sheets, these refer to any arbitrary piece of code which will be copied into the generated code for the selected property.

component

Strictly speaking, anything derived from java.awt.Component or java.awt.MenuComponent. Sometimes, the term is used more broadly to refer to objects derived from other Java classes.

constructor

The first method of a class which is called when a Class is created. The constructor is special in that the signature is unique (it has no return type) and it is always called for a new Class. If a subclass does not provide a constructor, the first such instance in the superclass hierarchy is called.

constraints

The properties of a component which control its size and positions. The constraints are dictated by the layout of the component's parent container.

container

Strictly speaking, anything derived from java.awt.Container.

containment hierarchy

In Visaj, the hierarchical view of the user interface which shows how objects relate to each other in terms of their parent->child relationship.

customizer

A dialog which sets properties on a Java bean. Not all beans have customizers; they have to be specially provided for a bean by the bean vendor.

design

In Visaj, the design is the user interface which is being created. Since any or all methods in a Class can have a user interface, the design may refer to individual methods or the whole class and includes the hierarchy of components plus any properties or variables.

double-click

Press and release the mouse button twice in quick succession.

drag and drop

The mechanism on window systems which allows information to be "carried" across the screen and moved or copied from one area to another by pressing a mouse button over the information, moving the mouse to another place and releasing the button. Different window systems have different ideas of which mouse button to use.

dynamic display

The window in Visaj which previews the user interface as it is being developed.

environment variable

UNIX and DOS shells run within an environment. Environment variables are variables which are set within a shell. Any applications run from that shell can use environment variables to set options and preferences. Java provides an interface for checking environment variables.

event bindings

In Visaj, the linking of objects using events. Event bindings provide dynamic functionality for your design.

events

In the Java model, events are actions, such as mouse clicks or list item selections. Objects which have registered themselves as listeners to other objects are notified of events occurring.

floating window

A window which is not attached to any other. Such a window may be moved and iconized independently of the window which caused it to be displayed. In Visaj, the dynamic display is an example of a floating window.

GUI builder

Graphical User Interface builder, as its name suggests, refers to a tool which allows you to build a user interface graphically.

IDE

An IDE (Integrated Development Environment) is an application which provides complete support for the building of an application. This would include a tool for defining the user interface, a tool for defining the files which make up the application, a compiler and a debugger. Some IDEs may include other tools too.

inset

The top, left, right and bottom margins of a container or component.

install directory

The root directory where your copy of Visaj was installed. You may need to know where this is in order to load example files for the tutorial. Any pathname for such files is relative to the directory where Visaj was installed.

internationalization

The setting of an application's strings (and other text) such that it may be altered easily to display in another language. Fetching strings from a pool, for example, means that only the strings in the pool need to be changed and not the application itself.

invisible bean

A Java bean which is not visible. All components (in the strict sense of the word) are capable of being displayed on the screen, but objects derived from other classes may not be.

JAR file

A Java archive file is a file which groups classes and resources so that they may be used by another application. A JAR file may be compressed. A JAR file also contains a manifest file which is a plain text file listing the contents of the archive.

Java Beans

Java Beans are reusable software components with a pre-defined API.

JFC

The JFC (Java Foundation Classes) are an extension to the AWT (Abstract Windowing Toolkit). They include a comprehensive set of graphical user interface class libraries, pluggable look and feel and the Accessibility API.

method design

All aspects of the design of a method, which includes the hierarchy of user interface objects, its signature and any event bindings. The left area of the Class Editor window contains all the editors for the design of a method.

method editors

The left area of the Class Editor window which contains tools for building the hierarchy of user interface objects, changing the method signature and setting up event bindings.

multiple selection

The selection of more then one object, specifically in the containment hierarchy of the Class Editor window.

mwt

Stands for Motif Widget Set. These widgets are provided with Visaj like the Diamonds. They are Java emulations of Motif widgets not available in the AWT set. They are described in Appendix  A, "Diamond Components", starting on page 191.

native methods

This is a Java term which refers to methods which are specific to one platform only and which are, therefore, not portable.

object

In the Java language, an object is the base class of all components. The term objects is used in Visaj to denote the basic building blocks of a user interface. See object palette.

object palette

The palette on the left of the Class Editor window containing the elements available for building a user interface.

package

A reserved word in the Java language, the package is the group to which a Class belongs. All classes belong to a package. The package name corresponds to the directory where the Class files reside. For example the package name java.awt.event corresponds to the directory java/awt/event1

portable code

Code which may be moved without difficulty from one platform to another and run.

properties

In Java, objects have properties which control all aspects of their appearance and behavior. Properties may be set and fetched by an application.

project

The "whole" application. A project includes the idea of all source files, image files and any extra data.

Pure Java

100% Pure Java is a trademark of Sun Microsystems. It is a standard which describes applications which are written completely in the Java language. To qualify for this description, applications must not use any native methods or import any classes which are not documented parts of the Java API. 100% Pure Java applications are guaranteed to be platform independent.

radio button behavior

The behavior of buttons when only one in a group can be selected. In Java, this applies to checkBoxes within a checkBoxGroup. The selected checkBox will stay set until another is selected.

resource bundle

A resource bundle contains the strings an application uses. Each string is identified by a key. Applications fetch strings from the resource bundle using the key as an indirection. With resource bundles for different languages, an application can far more easily be internationalized.

signature

In terms of a class or method in the Java language, the signature is the name, accessibility, scope and inheritance of a class or method. It also includes the parameters of a method. For example:

public Class MyFrame extends Frame

private boolean MyMethod(String s)

superclass

Also known as "base class", the superclass is the class from which a given class is derived. In the Java language, it is the class which follows the word "extends" in the class definition.

Swing

The GUI components written in the Java language, without

window-system-specific code, which form part of the JFC.

tabbed panel

A Diamond component which is like a stack of cards. Each card has a tab with the name of the card on it. Pressing the tab brings the associated card to the front. The method editors in the Class Editor window are arranged within a tabbed panel.

this

In the Java language, "this" is a reserved word and refers to the current class.

tree view

In Visaj there are two types of tree view: the containment hierarchy, which shows the relation between objects in terms of containments and the class structure, which provides a convenient way of grouping the elements of a Class.

variable name

In Visaj every object which makes up the user interface being created has a name. This name is generated into the code and provides a means of referring to the object. Use variable names which are meaningful to you if you are thinking of accessing objects.

variable scope

The scope of an object in Visaj defines how accessible it is - its visibility to other classes. An object (in Property Sheets they are also referred to as "variables") can be "public" - meaning that it is visible everywhere, "protected" - meaning that it is visible within its own class, all subclasses and all classes in the same package, "private" - meaning that it is only visible within its class or the default (when no keyword is given) - meaning that it is visible within its own class and package only.


1 This is the UNIX directory format. Windows programmers should replace the forward slash ("/") with the backward slash ("\").


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