String a; Point b;
a
?
a
is a reference to a String
object.b
?
b
is a reference to a Point object.null
ValueA reference variable holds information about the location of an object. It does not hold the object itself. This code
String a; Point b;
declares two reference variables but does not construct any objects. The following constructs objects and puts references in the variables:
a = "Elaine the fair" ; b = new Point( 23, 491 );
null
is a special value that means "no object."
Set a reference variable to null
when it is not referring to
any object.
Variables are often set to null
when they are declared:
String a = null; Point b = null;
(Thought Question:) Do you think that null
can be
assigned to reference variables of any type?
Click here for a .