Java Reference
In-Depth Information
Java syntax: Class definition
public class class-name {
declarations of methods and fields
Style Note
13.1, 13.1.3:
class name
conventions
}
Purpose : To define a new file drawer, named class-name , and describe
the contents of its manila folders (instances, or objects, of the class).
Note that the class definition does not include the clause “ extends ”. This
class does not explicitly extend another; it stands alone, by itself. The subclasses
of JFrame that we wrote in Chap. 1 extended JFrame .
A class definition defines the contents of manila folders that are placed in its
file drawer. Such a manila folder is called an instance of the class , or an object
of the class . An instance of class Employee appears in Fig. 3.2, along with the
file drawer in which the instance appears. Each instance of a class contains the
following components:
Style Note
13.1, 13.1.1:
field name
conventions
1. The fields , or instance variables , of the class, which are the variables
defined in it that do not have modifier static .
2. The instance methods of the class, which are the methods defined in it
that do not have modifier static .
Initial values of fields
If a field is declared without an initializing assignment, the field has a
default value, which depends on its type. Here are the default values:
Activity
3-4.2
byte: ( byte )0
float : 0.0F
short : ( short )0
double : 0.0D
int : 0
boolean : false
char : null character, '\u0000'
long: 0L
class-type : null
a0
Employee
getName()
setName(String)
getStart()
setStart( int )
getCompensation()
changeSalary( double )
toString()
Employee(String, int )
name
Gries
start
1997
salary
50,000
Figure 3.2:
An instance of class Employee
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