Glosary from Java knowledge base

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Glossary

abstract: A Java programming language keyword used in a class definition to specify that a class is not to be instantiated, but rather inherited by other classes
abstract: A keyword that means a class cannot be instantiated
abstract class: A class that can only be subclassed - it cannot be instantiated or the compiler will display an error message and refuse to compile the program
abstract method: A method with no implementation
Abstract Windowing Toolkit (AWT): A collection of graphical user interface (GUI) components that were implemented using native-platform versions of the components
access modifier (access specifier, visibility modifier): A keyword that specifies how restricted the access is to a class or interface or variable or method
access unit: A syntactic unit to which access can be controlled with an access modifier
accessor method: A method which returns (getter) or changes (setter, mutator) the state of an object
ancestor (ascendant, ascendant class): A class A is an ancestor of class B if it is farther up in the class hierarchy than class B and class B is descended from it
applet (Java applet): A program that adheres to certain conventions that allow it to run within a Java-enabled browser
application (Java application): A Java program that does not run in a Web browser
Application Programming Interface (API): The specification of how a programmer writing an application accesses the behaviour and state of classes and objects
array: A collection of data items that are all of the same type, in which each item's position is uniquely designated by an integer
assignment expression: An expression that contains an assignment operator
assignment operator: An operator that performs assignment to the variable on the left and returns the value of the expression on the right
attribute: a simple piece of data used to represent the properties of an object
behaviour: The set of all responses to all possible messages
behaviour: The way an object or system acts and reacts, possibly changing its state
binary operator: An operator that has 2 arguments
binary operator: An operator that has two operands
bitwise operator: An operator that performs a boolean operation bit by bit on two integral types of the same length
block: A syntactic unit that groups statements or makes new declarations
block: Any code between matching braces
body: A block that is not nested inside another block
boolean expression: An expression that produces a true or false result
bytecode: Machine-independent code generated by the Java compiler and executed by the Java interpreter
bytecode verifier: A verifier that is part of the Class File verifier and which performs a data-flow analysis on the actual bytecode stream that is contained in each method definition in the class .
casting: The process of producing a new value that has a different type than its source
checked exception: A kind of exception that Java checks for at compile time and for which a Java program contains handlers
class: A blueprint (prototype) that defines (the variables and the methods) common to all objects of a certain kind
class: A software module that provides both procedural and data abstraction. It describes a set of similar objects, called its instances
class: A specification that defines variables and methods common to a set of all objects of a certain kind
class: A template that describes the data and behaviour of its instances called objects
class body (class definition block): A block that specifies the variable declarations, the methods and the constructors for the class
class declaration: A declaration that specifies a class and does not include the class body
class definition: A definition that specifies a class and includes the class body
class file: A file that contains Java bytecodes
class hierarchy: A hierarchy of classes
class member (static member): A member of a class which is either a field or a method
class method (static method): A method that is invoked without reference to a particular object
class method (static method): A method that, unlike an instance method, does not execute in the context of a particular instance of a class
class path: An ordered list of directories or zip files to search for class files
class type: A reference type that is defined by a class, i.e. its values are the class instances
class variable (static field, static member variable, static variable): A data item present in a class that is shared by all instances of that class
class^2: A keyword that must be in a class declaration
clone: A method that creates objects from other objects of the same type
code: Computer programming instructions
collection: A group of things
compilation: The process of translating higher level code, usually source code (or bytecode) , into lower level code
compiler (Java compiler): A program to translate Java source code into code to be executed by a computer
compound expression: An expression made up of two or more expressions
concrete class: A class that can have instances
condition: A condition in Java is a statement that evaluates to a boolean value (true or false)
constant (constant variable, final variable): A variable with a value that never changes
constructor: A procedure that is called whenever a new object is created
core API: The API included in every full implementation of the Java platform
core class: A public class (or interface) that is a standard member of the Java Platform
current object: The object whose method is currently being called
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)
default access of a class: The access mode of a class that is not declared public; access is limited to the package in which the class was declared
default access of a method or variable: The access mode of methods or variables that do not have an explicit access modifier; access is limited to objects in the same class (and subclasses in the same package), in the same compilation unit, and in the same package
default constructor: A constructor that is automatically provided by the runtime system for any class that contains no explicit constructors
default package: An unnamed package that contains class files whose source files did not contain a package statement
definition: A statement that reserves storage (for data) or provides implementation (for methods).
deprecated method: A method that has been replaced by a different method in a later version of Java
descendent: A class A is a descendent of class B if it is lower down in the class hierarchy than class B and class B is an ancestor of it
descendent: A class that inherits from another
dialog (dialog box): A specific window with which a user can interact, but which is not the main UI window
dynamic binding (late binding, virtual binding): A mechanism by which, when the compiler can't determine which method implementation to use in advance, the runtime system (JVM) selects the appropriate method at runtime, based on the class of the object
dynamic binding (late binding, virtual binding): The process of binding a call to a particular method. This is performed dynamically at run-time due to the presence of polymorphism
encapsulation: Creating a module to contain some algorithm or data structure, thus hiding its details behind the module's interface
environment: The hardware and software configuration of a computer
equals: A method that compares two objects for equality
error: An exception that is exempted from compile-time checking because it can occur at many points in the program and recovery from them is difficult or impossible . A Java program declaring such exceptions would be cluttered, pointlessly.
exception: An event that happens during program execution that prevents the program from continuing normally; generally, an error
executable code: Code that can be executed by a computer
expression: A series of variables, operators and method calls (constructed according to the syntax of the language) that evaluates to a single value
expression statement: An expression followed by a semicolon
extends: A keyword that indicates a class is a subclass of another class or an interface is a subinterface of another interface
file: A block of information in the form of bytes, stored together on a computer or external digital storage medium, and given a name
final class: A class that cannot have subclasses
final method: A method that cannot be hidden or overridden
finalize method: A method that is invoked before an object is discarded by the garbage collector, allowing it to clean up its state
fully qualified name (long name): A name that is unambiguous
garbage collection: A mechanism which checks for objects that are no longer reachable from any executable code and reclaims the space used by them
get method (getter): A method that returns the value of an instance variable
get method (getter): A method which returns the state of an object
graphical user interface (GUI): An interface that uses graphics, along with a keyboard and a mouse, to provide an easy-to-use interface for users to interact with a program
GUI event object: A common object used in GUI window systems to represent the action of a user pressing a mouse button or a key on the keyboard
hierarchy: An organized tree-like structure of subjects
HotSpot: An add-on performance module for the JavaTM 2 SDK
HTML Converter: An application that converts and existing web page so that all its applets are run by the Java Plug-in
HTML tag: A code in an HTML document that may serve various functions such as controlling the styling of text and placement of graphic elements and providing links to interactive programs and scripts.
identity: Unlike primitive values, objects possess a unique identity that makes them distinguishable from one another, even when they are in the same state ; e.g. Two strings, s1="x" and s2=new String(s1), are equal but have different identity, so s1.equals(s2) is true but s1==s2 is false.
implements: A keyword that declares that your class implements one or more interfaces
import statement (import declaration): A statement that permits using references to other packages without prefixes
information hiding: Hiding details so as to reduce complexity
inheritance: A mechanism that enables one class to inherit all the behaviour and attributes of another class
inheritance: The acquisition of data (variables) and behaviour (methods) from a parent (superclass) in a hierarchy
inheritance: The possession by one class of elements defined in another class, by virtue of the fact that the former class is defined to be a subclass of (to extend) the latter
inner class: A nested class whose instance exists within an instance of its enclosing class and has direct access to the instance members of its enclosing instance
instance method: A method that executes in the context of a particular object; it has access to the instance variables of the given object, and can refer to the object itself using the 'this' keyword
instance method: Any method that is invoked with respect to an instance of a class
instance variable (data member, field, object variable): A data item present in all the instances of a class, normally used to implement associations and attributes
instance variable (data member, field, object variable): Any item of data that is associated with a particular object.
instantiation: The process of creating a new instance of a class
interface (abstract data type): A named collection of method declarations (without implementations), may also include constant declarations (variables marked static and final)
interface (abstract data type): In Java, a software module containing a description of a set of operations that certain classes must implement
interface body: One of two parts of an interface definition (the other part is the interface declaration)
interface hierarchy: A hierarchy of interfaces
interface^2: A Java language keyword used to define a collection of method definitions and constant values
invocation: The process of calling a method , i.e., executing its body, passing arguments to be associated with the method's formal parameters.
jar (Java Archive Tool): A tool included in the SDK that can pack files into Java Archive files as well as unpack them
Java: An object-oriented programming language developed by Sun Microsystems
Java API: A large collection of ready-made software components that provide many useful capabilities, such as graphical user interface ( GUI ) widgets
Java Archive file (jar file): A collection of Java classes and other files packaged into a single file
Java Debugger (jdb): A command line debugger for Java classes
Java Development Kit (JDK): A comprehensive set of tools, utilities, documentation and sample code for developing programs
Java interpreter (Java application launcher): A module that alternately decodes and executes every statement in some body of code
Java Plug-in: A free browser add-on that supports the latest version of Java
Java program (program): A collection of 1 or more classes that work together and is started either by the operating system or a browser running it
Java Runtime Environment (JRE): The runtime part of the Java Development Kit
Java Virtual Machine (Java VM): A program that implements the theoretical concept of the Java Virtual Machine
Java Virtual Machine (Java VM): An architecture-neutral and portable language platform of Java
Java-compatible Web browser: A Web browser that can display Java applets
java.applet: A package that contains applet classes
java.awt: A package that contains GUI widget classes
java.io: A package that contains input and output classes
JIT compiler (Just-in-time compiler): A compiler that converts all of the bytecode into native machine code just as a program is run
just-in-time compilation (JITC): A kind of compilation that converts a method into machine code the first time it is executed and stores the machine code to save work on subsequent calls
keyword: A word that has special meaning in Java
leaf class: A class at the very bottom of an inheritance hierarchy
literal: A value that appears explicitly in a program
local variable: A data item known within a block but inaccessible to code outside the block
local variable: A variable that is declared in a method
main class: The class which contains the main method and whose name is specified as an argument to the Java interpreter
main method: A method that is initially executed in an application
member: A field (instance variable) or method of a class
member of a package: A class or interface belonging to a package
message: A means of communication between objects
method (function, member function): A concrete implementation of an operation; a procedure in a class
method (function, member function): A function defined in a class
method (function, member function): A procedural abstraction used to implement the behaviour of a class
method (function, member function): Code that specifies some of the behaviour of a class or instance
method body: One of two parts of an method definition (the other part is the method declaration)
method name overloading (method overloading): A mechanism that allows several methods to have the same name as long as they have different method signatures
method overriding (hiding, overriding, overshadowing): The process of providing a more specialized implementation for the method
method signature (header): The method's name and the number of its parameters and the types of its parameters
modal dialog: A dialog that the user must dismiss before interacting with any other window. While in the modal dialog, the system is in a very restrictive mode
modular program: A program divided into units that can be developed and maintained independently
multiple inheritance: Inheritance from more than one superclass
multithreading: A mechanism that provides support for multiple threads of execution to run concurrently within a program without interfering with each other
named constant: A constant that has a name
native: A keyword that indicates that the method code is not written in Java
nested block: A block that is nested inside another block
nested class: A class that is a member of another class
new operator (creation operator): An operator that creates a new object (allocates space for it).
non-modal dialog: A separate window that the user can choose to interact with, but does not have to
object (instance): A data element in an object-oriented system, which has its own identity, belongs to a particular class, and has behaviour and properties
object (instance): A piece of memory that holds data in instance variables and a pointer to its class
object (instance): A software bundle of variables and related methods
Object class: A class that is at the top of the class hierarchy
object creation expression: An expression that creates a new object
object reference (handle, reference): A variable that refers to an object
object serialization: The ability to write the complete state of an object (including any objects it refers to) to an output stream, and then recreate that object at some later time by reading its serialized state from an input stream
object table: A table that maps object handles to actual addresses
object-oriented paradigm: An approach to software design and programming in which software is primarily thought of as a collection of classes that each have responsibilities for various operations, and which are instantiated at run time to create objects
object-oriented programming: A way of conceptualizing a computer program as a set of separate objects that interact with each other
object-oriented programming language: A programming language in which each data item with the operations used on it is designated as an object; the routines used to operate on the data item are called methods; and objects are grouped in a hierarchy of classes, with each class inheriting characteristics from the class above it
operand (argument of an operator): An input to an operator
operation: a higher-level procedural abstraction than a method: It is used to discuss and specify a type of behaviour, independently of any code which implements that behaviour
operator: A built-in method that works on inputs supplied to it according to the conventions of arithmetic
operator: A symbol used for arithmetic and logical operations
package: A collection of related classes and interfaces that provides access protection and namespace management
package statement (package declaration, package declaration): A statement that declares the name of the package the file defines
parameter (argument, formal parameter): A variable that transmits a primitive datum or object reference to a method or constructor
part-whole relation: The relation expressed by "has a"
platform: The hardware or software environment in which a program runs
pointer: A variable that is used to store an address
polymorphic operation: An operation where the program decides, every time an operation is called, which of several identically-named methods to invoke
polymorphism: A property of object oriented software by which an abstract operation may be performed in different ways in different classes
polymorphism: The ability to use the same syntax for objects of different types
primitive type: A type where a variable of that type evaluates to the value stored in the variable
private: A keyword that means a variable or method is only accessible within its class
private access: The access mode of methods or variables specified by the keyword "private"; access is limited to objects in the same class only
private variable: A variable declared with the private access modifier
protected: A keyword that indicates that a method or variable may be accessed by any object in the same class (and its subclasses including those in a different compilation unit in another package), by all objects in the same compilation unit, and by all objects in the same package
protected access: The access mode of methods or variables specified by the keyword "private"; access is limited to objects in the same class (and subclasses in any package), in the same compilation unit, and in the same package
public: A keyword that indicates that a method, class or variable may be accessed by any object
public access: The access mode of classes, methods or variables specified by the keyword "public"; access is granted to any object
public interface: A class's public instance variables and public instance methods which are accessible to objects outside the class
public variable: A variable declared with the public access modifier
recursion: A mechanism in which a method calls itself
recursive method: A method that calls itself
reference type (non-primitive type): A type where a variable of that type evaluates to the address of the location in memory where the object referenced by the variable is stored
reuse: The practice of using the same code or design in more than one place
runtime system: The software environment in which programs compiled for the Java virtual machine can run
scope: The region of a source text over which a declaration holds
scope of a variable: The block of code within which the variable is accessible and determines when the variable is created and destroyed
scoping unit: A syntactic unit that defines a scope (the region of a source text over which a declaration holds)
server: An application that serves clients on a network
set method (mutator, setter): a method that assigns a value to an instance variable
set method (mutator, setter): A method which changes the state of an object
single inheritance: Inheritance from only one superclass
source code: Code that is written by a person
source file: A file that contains source code
specification: A detailed precise presentation of something or of a plan or proposal for something
state: How something is; its configuration, attributes, condition, or information content
statement: A syntactic unit that defines a step in the execution of a program
static: A keyword that means a variable or method belongs to the class and not to the instances
static binding: A mechanism by which the compiler determines which method implementation to use in advance, based on the type of the reference (regardless of the actual class of the object)
stream: A sequence of objects
string literal (literal string): A string of characters between double quotation marks
subclass: A class that is an extension of another class, and hence inherits from the other class
subclass-superclass relation: The relation expressed by "is a"
subclassing: The process of creating a new class that inherits from an existing class
super: A Java language keyword that allows a method to refer to hidden variables and overridden methods of the superclass
super: A keyword that refers to the superclass of an object
superclass (parent class): A class of which another class is an extension, and hence defines properties that are inherited by the other class
superclass (parent class): A class's direct ancestor
symbol: A character or string of characters that represents or stands for something else
synchronization: A mechanism to guarantee that only one thread can access an object at a time
synonym: One of two or more words or expressions that have the same meaning
syntactic unit: A part of a program to which a syntax rule applies
System: A class that is part of the API of Java and which provides system-independent access to system-dependent functionality
tertiary operator: An operator that has 3 arguments
this: A keyword that refers to the current object or is used instead of the class name as the constructor name
thread (lightweight process): An object used in multithreaded software systems that represents a sequence of program execution
Thread class: A Java class that implements the general concept of a thread
thread priority: The importance of a thread, which determines which thread in a system will be run first
type (data type): A class, interface, or primitive type
unary operator: An operator that has 1 argument
unchecked exception: An exception that is not checked , which is of the class RuntimeException and its subclasses, or of the class Error and its subclasses
uninitialized object: An object that has been declared but has not been assigned a value
user interface component (widget): A component used to create the user interface such as a menu, list, input field etc.
variable: An item of data named by an identifier
virtual machine (VM): An abstract specification for a computing device that can be implemented in different ways, in software or hardware
void: A keyword that indicates that a method returns no result
Web browser (browser): A software application that enables you to access the World Wide Web