Java Reference
In-Depth Information
Constructor
-Aspecial kind of method called when an object is created. Its job is to
carry out initialization tasks.
The class
GenericClass
below illustrates these features:
public class
GenericClass
{
int i;
This field declares the
property i as an integer
type. (By default its
value will be 0.)
public GenericClass (int j) {
i = j;
A constructor is called
when an instance of this
class is first created.
It can be used to
initialize properties
.
}
public void set (int j) (
This method assigns a
value to the field i
.
i = j;
}
public int get ()
{
This method returns the
value of i
.
return i;
}
}
We can now create an instance of our new data type and invoke its methods:
void aMethodSomewhere () {
// Create an instance of this data type.
GenericClass g
=
new GenericClass (5);
int k
=
g.get ();
...
In the following pages we discuss the main features of a class definition, beginning
with data fields.
3.3.1 Data fields
A class definition typically includes one or more fields that declare data of various
types. Data fields are also called “member variables.” For example, this code
shows a class with a single primitive
int
data value:
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