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syntactic unit > access unit > variable > pointer > object reference > named object reference > null

null
subject			fact

null	does not have a type
	is a subtopic of Variables and Data Types
	is a kind of named object reference
	represents an invalid or uncreated object
object reference	has purpose to refer to an object indirectly so the object may be moved or reclaimed
	is a key into the object table
	is a label for a chunk of memory that holds the memory address for a chunk of memory that holds and instance
	is not accessible to the programmer except for the equals method
	to cascade you prepend a class or package names to a reference with the character '.'
variable	can be accessed by other variables and methods in any class in the same package by default
	can contain different classes of objects depending on the type of the variable
	can contain only values that are of the same type as the variable or a subtype of the variable's type
	can refer to a particular object, several different objects during the execution of a program, or no object at all
	has scope
	has part value
	is declared by giving the data type followed by the name of the variable
	is destroyed in the block where it is declared
	may have access modifier public or private or protected
	refers to a class or an object or a primitive datum
access unit	has access mode
syntactic unit	has syntax rule bold = mandatory italic = non-terminal normal font = optional

Up: named object reference