Discovering Classes and Objects - Beginning Java 7 - page 75

Declaring and Accessing Instance Fields
You can declare an instance field by minimally specifying a type name, followed by
an identifier that names the field, followed by a semicolon character ( ; ). Listing 2-3
presents a Car class with three instance field declarations.
Listing 2-3. Declaring a Car class with make , model , and numDoors instance fields
class Car
{
String make;
String model;
int numDoors;
}
Listing 2-3 declares two String instance fields named make and model . It also
declaresan int instancefieldnamed numDoors .Byconvention,afield'snamebegins
withalowercaseletter,andthefirstletterofeachsubsequentwordinamultiwordfield
name is capitalized.
Whenanobjectiscreated,instancefieldsareinitializedtodefaultzerovalues,which
youinterpretatthesourcecodelevelasliteralvalue false , '\u0000' , 0 , 0L , 0.0 ,
0.0F , or null (depending on element type). For example, if you were to execute
Car car = new Car(); , make and model would be initialized to null and
numDoors would be initialized to 0 .
Youcanassignvaluestoorreadvaluesfromanobject'sinstancefieldsbyusingthe
member access operator ( . ); the left operand specifies the object's reference and the
rightoperandspecifiestheinstancefieldtobeaccessed. Listing2-4 usesthisoperatorto
initialize a Car object's make , model , and numDoors instance fields.
Listing 2-4. Initializing a Car object's instance fields
class Car
{
String make;
String model;
int numDoors;
public static void main(String[] args)
{
Car car = new Car();