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subclass
subject			fact

subclass	if a subclass declares a method with the same name as a superclass's method then the subclass's method overrides the superclass's method
	if a subclass is in the same package as its superclass then the subclass inherits all members declared with no access modifier
	subclass inherits all of the members in its superclass unless the subclass hides a member variable or unless the subclass overrides a method
	subclass must override any method that is declared abstract in the superclass or the subclass must be declared abstract
	can access hidden member variables using the keyword super
	can access overridden methods using the keyword super
	can hide an inherited member variable by declaring a member variable with the same name
	can override an inherited method by defining a method with the same signature
	can use any member that is inherited
	cannot be defined until its direct superclass has been defined
	cannot override any class method (a method that is declared static in the superclass)
	cannot override any method that is declared final in the superclass
	has definition A class that is an extension of another class, and hence inherits from the other class
	does not inherit constructor
	does not inherit the private members of its superclass
	has example of creation public class Movie extends Attraction
	inherits 0 or more methods from its superclass and all of its ancestors
	inherits 0 or more variables from its superclass and all of its ancestors
	inherits all instance variables and methods defined in its ancestor classes
	inherits all package members of its ancestors
	inherits all protected members of its ancestors
	inherits all public members of its ancestors
	inherits none, some or all of its behaviour from all its ancestors
	inherits none, some or all of its state from all its ancestors
	is a subtopic of Classes
	is created using the extends keyword
	is a kind of descendent
class	adds 0 or more variables to the variables it inherits from its superclass
	adds 0 or more methods to the methods it inherits from its superclass
	can be imported from a package
	can extend only one superclass
	can have a main method
	can have instances
	can have more than one constructor each of which has different sets of arguments
	can have the same name as another class if the two classes are not in the same package and their packages are never imported into the same file
	can implement more than one interface
	can protect its members from access by other classes or objects using an access modifier
	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
	has a fully qualified name that includes its package name and a simple name that does not include its package name
	has 0 or more subclasses
	has 1 superclass except Object class which has no superclass
	has behaviour that is specified by its instance methods
	has more specialized behaviour than a class farther up in the class hierarchy
	has public interface which contains its public instance variables and instance methods
	has benefit reusability modularity
	has example public class HelloWorld { public static void main(String[] args) { System.out.println("Hello World!"); } }
	has part class name
	has part code
	has part constructor
	has syntax class classname { // declarations of variables // declarations of constructors // declarations of other methods with public ones first }
	is abstract if it has one or more abstract methods
	is the unit of data abstraction in an object-oriented program
	is a descendant of Object class
	is specified by 1 class definition
	may have access modifier public or private or protected
	provides implementation for all its instance methods unless the class is abstract
	represents several similar objects
	should be a member of 1 named package rather than the default package
	should be named after a thing its instances represent in the real world
	should be placed in its own source file
	should have a comment at the top describing the purpose of the class, how it should be used, its authors and its history of modification
	should have a unique name since somebody in the future might want to import the packages containing both classes and hence create a name clash
	should not be named after the internals of a computer system such as 'Record', 'Table', 'Data', 'Structure', or 'Information'
	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
	to instantiate you create an instance of it
access unit	has access mode
syntactic unit	has syntax rule bold = mandatory italic = non-terminal normal font = optional

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