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Java abstract class
subject			fact

Java abstract class	has one or more abstract methods
	is a subtopic of The Basics of Java
	is created by specifying the abstract keyword on the first line when you declare the class
	is a kind of abstract class
	is a kind of Java class
abstract class	has purpose to hold features that will be inherited by two or more subclasses
	has part abstract method
Java class	can extend only one superclass
	can implement more than one interface
	has form class classname { // declarations of variables // declarations of constructors (discussed below) // declarations of other methods with public ones first }
	is abstract if it has one or more abstract methods
	is stored in a file of the same name
	may implement particular low-level subsystems
	should be placed in its own source file
	should order elements as follows: class variables instance variables constructors the most important public methods methods that are simply used to access variables private methods
	uses an implements clause to declare that it contains methods for each of the operations specified by the interface
class	contains all of the code that relates to its objects including code describing how the objects of the class are structured - i.e. the data stored in each object that implement the properties The procedures, called methods, that implement the behaviour of the objects
	contains data associated with each object
	declares a list of variables, called instance variables, corresponding to data that will be present in each instance
	is divided up into methods
	is drawn as a box with the name of the class inside in a UML class diagram
	is needed in a domain model if you have to store or manipulate instances of it in order to implement a requirement
	represents several similar objects
	see also class^2
	should be created to hold a responsibility if the responsibility cannot be attributed to any of the existing classes
	should be named after things their instances represent in the real world
	should not be named after the internals of a computer system such as 'Record', 'Table', 'Data', 'Structure', or 'Information'
data abstraction	groups the pieces of data that describe some entity, so that programmers can manipulate that data as a unit
	helps a programmer to cope with the complexity of data
	hides the details of data
module	has high cohesion if related aspects of a system are kept together in this module, and unrelated aspects are kept out
	lacks side effects if it does not modify any data, and does not leave behind any information, other than its result, that would have an effect on other computations
component	may perform a special-purpose function such as the user interface for a particular system

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