Java Vocab

implements

A Java keyword included in the class declaration to specify any interfaces that are implemented by the current class.

default

A Java keyword optionally used after all case conditions in a switch statement. If all case conditions are not matched by the value of the switch variable, the default keyword will be executed.

case

A Java keyword that defines a group of statements to begin executing if a value specified matches the value defined by a preceding switch keyword.

finally

A Java keyword that executes a block of statements regardless of whether a Java Exception, or run time error, occurred in a block defined previously by the try keyword.

import

A Java keyword used at the beginning of a source file that can specify classes or entire packages to be referred to later without including their package names in the reference.

abstract

A Java keyword used in a class definition to specify that a class is not to be instantiated, but rather inherited by other classes. An abstract class can have abstract methods that are not implemented in the abstract class, but in subclasses.

if

A Java keyword used to conduct a conditional test and execute a block of statements if the test evaluates to true.

catch

A Java keyword used to declare a block of statements to be executed in the event that a Java exception, or run time error, occurs in a preceding try block.

for

A Java keyword used to declare a loop that reiterates statements. The programmer can specify the statements to be executed, exit conditions, and initialization variables for the loop.

do

A Java keyword used to declare a loop that will iterate a block of statements. The loop's exit condition can be specified with the while keyword.

char

A Java keyword used to declare a variable of type character.

enum

A Java keyword used to declare an enumerated type.

float

A Java keyword used to define a floating point number variable.

double

A Java keyword used to define a variable of type double.

else

A Java keyword used to execute a block of statements in the case that the test condition with the if keyword evaluates to false.

continue

A Java keyword used to resume program execution at the end of the current loop. If followed by a label, continue resumes execution where the label occurs.

break

A Java keyword used to resume program execution at the statement immediately following the current statement. If followed by a label, the program resumes execution at the labeled statement.

final

A Java keyword. You define an entity once and cannot change it or derive from it later. More specifically: a final class cannot be subclassed, a final method cannot be overridden and a final variable cannot change from its initialized value.

exception handler

A block of code that reacts to a specific type of exception. If the exception is for an error that the program can recover from, the program can resume executing after the exception handler has executed.

abstract class

A class that contains one or more abstract methods, and therefore can never be instantiated. Abstract classes are defined so that other classes can extend them and make them concrete by implementing the abstract methods.

generic

A class, interface, or method that declares one or more type variables. These type variables are known as type parameters. A generic declaration defines a set of parameterized types, one for each possible invocation of the type parameter section. At runtime, all of these parameterized types share the same class, interface, or method.

hierarchy

A classification of relationships in which each item except the top one (known as the root) is a specialized form of the item above it. Each item can have one or more items below it in the hierarchy. In the Java class hierarchy, the root is the Object class.

array

A collection of data items, all of the same type, in which each item's position is uniquely designated by an integer.

Abstract Window Toolkit (AWT)

A collection of graphical user interface (GUI) components that were implemented using native-platform versions of the components. These components provide that subset of functionality which is common to all native platforms. Largely supplanted by the Project Swing component set. See also Swing.

group

A collection of principals within a given security policy domain.

applet

A component that typically executes in a Web browser, but can execute in a variety of other applications or devices that support the applet programming model.

class variable

A data item associated with a particular class as a whole--not with particular instances of the class. Class variables are defined in class definitions. Also called a static field. See also instance variable.

argument

A data item specified in a method call. An argument can be a literal value, a variable, or an expression.

field

A data member of a class. Unless specified otherwise, a field is not static.

definition

A declaration that reserves storage (for data) or provides implementation (for methods). See also declaration.

abstract method

A method that has no implementation.

class method

A method that is invoked without reference to a particular object. Class methods affect the class as a whole, not a particular instance of the class. Also called a static method. See also instance method.

compiler

A program to translate source code into code to be executed by a computer. The Java compiler translates source code written in the Java programming language into bytecode for the Java virtual machine1. See also interpreter.

constructor

A pseudo-method that creates an object. In the Java programming language, constructors are instance methods with the same name as their class. Constructors are invoked using the new keyword.

core class

A public class (or interface) that is a standard member of the Java Platform. The intent is that the core classes for the Java platform, at minimum, are available on all operating systems where the Java platform runs. A program written entirely in the Java programming language relies only on core classes, meaning it can run anywhere. .

const

A reserved Java keyword not used by current versions of the Java programming language.

bean

A reusable software component that conforms to certain design and naming conventions. The conventions enable beans to be easily combined to create an application using tools that understand the conventions.

critical section

A segment of code in which a thread uses resources (such as certain instance variables) that can be used by other threads, but that must not be used by them at the same time.

byte

A sequence of eight bits. Java provides a corresponding byte type.

declaration

A statement that establishes an identifier and associates attributes with it, without necessarily reserving its storage (for data) or providing the implementation (for methods). See also definition.

instanceof

A two-argument Java keyword that tests whether the runtime type of its first argument is assignment compatible with its second argument.

enumerated type

A type whose legal values consist of a fixed set of constants.

ASCII

American Standard Code for Information Interchange. A standard assignment of 7-bit numeric codes to characters. See also Unicode.

impersonation

An act whereby one entity assumes the identity and privileges of another entity without restrictions and without any indication visible to the recipients of the impersonator's calls that delegation has taken place. Impersonation is a case of simple delegation.

delegation

An act whereby one principal authorizes another principal to use its identity or privileges with some restrictions.

distributed application

An application made up of distinct components running in separate runtime environments, usually on different platforms connected through a network. Typical distributed applications are two-tier (client/server), three-tier (client/middleware/server), and n-tier (client/multiple middleware/multiple servers).

executable content

An application that runs from within an HTML file. See also applet.

classpath

An environmental variable which tells the Java virtual machine1 and Java technology-based applications where to find the class libraries, including user-defined class libraries.

exception

An event during program execution that prevents the program from continuing normally; generally, an error. The Java programming language supports exceptions with the try, catch, and throw keywords. See also exception handler.

instance

An object of a particular class. In programs written in the Java programming language, an instance of a class is created using the new operator followed by the class name.

binary operator

An operator that has two arguments.

bitwise operator

An operator that manipulates the bits of one or more of its operands individually and in parallel. Examples include the binary logical operators (&, |, ^), the binary shift operators (<<, >>, >>>) and the unary one's complement operator (~).

instance variable

Any item of data that is associated with a particular object. Each instance of a class has its own copy of the instance variables defined in the class. Also called a field. See also class variable.

instance method

Any method that is invoked with respect to an instance of a class. Also called simply a method. See also class method.

API

Application Programming Interface. The specification of how a programmer writing an application accesses the behavior and state of classes and objects.

autoboxing

Automatic conversion between reference and primitive types.

extends

Class X extends class Y to add functionality, either by adding fields or methods to class Y, or by overriding methods of class Y. An interface extends another interface by adding methods. Class X is said to be a subclass of class Y. See also derived from.

derived from

Class X is "derived from" class Y if class X extends class Y. See also subclass, superclass.

CORBA

Common Object Request Broker Architecture. A language independent, distributed object model specified by the Object Management Group (OMG).

DOM

Document Object Model. A tree of objects with interfaces for traversing the tree and writing an XML version of it, as defined by the W3C specification.

DTD

Document Type Definition. A description of the structure and properties of a class of XML files.

casting

Explicit conversion from one data type to another.

FTP

File Transfer Protocol. FTP, which is based on TCP/IP, enables the fetching and storing of files between hosts on the Internet. See also TCP/IP.

GUI

Graphical User Interface. Refers to the techniques involved in using graphics, along with a keyboard and a mouse, to provide an easy-to-use interface to some program.

HTML

HyperText Markup Language. This is a file format, based on SGML, for hypertext documents on the Internet. It is very simple and allows for the embedding of images, sounds, video streams, form fields and simple text formatting. References to other objects are embedded using URLs.

HTTPS

HyperText Transfer Protocol layered over the SSL protocol.

HTTP

HyperText Transfer Protocol. The Internet protocol, based on TCP/IP, used to fetch hypertext objects from remote hosts. See also TCP/IP.

comment

In a program, explanatory text that is ignored by the compiler. In programs written in the Java programming language, comments are delimited using // or /*...*/.

double precision

In the Java programming language specification, describes a floating point number that holds 64 bits of data. See also single precision.

class

In the Java programming language, a type that defines the implementation of a particular kind of object. A class definition defines instance and class variables and methods, as well as specifying the interfaces the class implements and the immediate superclass of the class. If the superclass is not explicitly specified, the superclass will implicitly be Object.

block

In the Java programming language, any code between matching braces. Example: { x = 1; }.

client

In the client/server model of communications, the client is a process that remotely accesses resources of a compute server, such as compute power and large memory capacity.

IDL

Interface Definition Language. APIs written in the Java programming language that provide standards-based interoperability and connectivity with CORBA (Common Object Request Broker Architecture).

IIOP

Internet Inter-ORB Protocol. A protocol used for communication between CORBA object request brokers.

bytecode

Machine-independent code generated by the Java compiler and executed by the Java interpreter.

deprecation

Refers to a class, interface, constructor, method or field that is no longer recommended, and may cease to exist in a future version.

boolean

Refers to an expression or variable that can have only a true or false value. The Java programming language provides the boolean type and the literal values true and false.

atomic

Refers to an operation that is never interrupted or left in an incomplete state under any circumstance.

distributed

Running in more than one address space.

authorization

See access control.

ACID

The acronym for the four properties guaranteed by transactions: atomicity, consistency, isolation, and durability.

actual parameter list

The arguments specified in a particular method call. See also formal parameter list.

garbage collection

The automatic detection and freeing of memory that is no longer in use. The Java runtime system performs garbage collection so that programmers never explicitly free objects.

Embedded Java Technology

The availability of Java 2 Platform, Micro Edition technology under a restrictive license agreement that allows a licensee to leverage certain Java technologies to create and deploy a closed-box application that exposes no APIs.

inheritance

The concept of classes automatically containing the variables and methods defined in their supertypes. See also superclass, subclass.

conversational state

The field values of a session bean plus the transitive closure of the objects reachable from the bean's fields. The transitive closure of a bean is defined in terms of the serialization protocol for the Java programming language, that is, the fields that would be stored by serializing the bean instance.

credentials

The information describing the security attributes of a principal. Credentials can be acquired only through authentication or delegation.

encapsulation

The localization of knowledge within a module. Because objects encapsulate data and implementation, the user of an object can view the object as a black box that provides services. Instance variables and methods can be added, deleted, or changed, but as long as the services provided by the object remain the same, code that uses the object can continue to use it without being rewritten. See also instance variable, instance method.

access control

The methods by which interactions with resources are limited to collections of users or programs for the purpose of enforcing integrity, confidentiality, or availability constraints.

identifier

The name of an item in a program written in the Java programming language.

hexadecimal

The numbering system that uses 16 as its base. The marks 0-9 and a-f (or equivalently A-F) represent the digits 0 through 15. In programs written in the Java programming language, hexadecimal numbers must be preceded with 0x. See also octal.

formal parameter list

The parameters specified in the definition of a particular method. See also actual parameter list.

commit

The point in a transaction when all updates to any resources involved in the transaction are made permanent.

authentication

The process by which an entity proves to another entity that it is acting on behalf of a specific identity.

compositing

The process of superimposing one image on another to create a single image.

core packages

The required set of APIs in a Java platform edition which must be supported in any and all compatible implementations.

bit

The smallest unit of information in a computer, with a value of either 0 or 1.

compilation unit

The smallest unit of source code that can be compiled. In the current implementation of the Java platform, the compilation unit is a file.

goto

This is a reserved Java keyword. However, it is not used by current versions of the Java programming language.

codebase

Works together with the code attribute in the <APPLET> tag to give a complete specification of where to find the main applet class file: code specifies the name of the file, and codebase specifies the URL of the directory containing the file.