String a; Point b;
Answer:
- What is the data type of the variable
a?ais a reference to aStringobject.
- What is the data type of the variable
b?bis a reference to a Point object.
- How many objects are there (so far)?
- So far, there are no objects, just variables that can reference objects, once there are some.
The null Value
A 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."
Your program should set a reference variable to null when it is not referring to
any object.
Programs often set variables to null when they are declared:
String a = null; Point b = null;
QUESTION 4:
(Thought Question:) Do you think that null can be
assigned to reference variables of any type?
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