Java Reference
In-Depth Information
Point() { super(); x = 1; y = 1; }
Therefore, the constructor for
Object
which takes no arguments is invoked.
The class
Object
has no superclass, so the recursion terminates here. Next, any instance
initializers and instance variable initializers of
Object
are invoked. Next, the body of
the constructor of
Object
that takes no arguments is executed. No such constructor is
declared in
Object
, so the Java compiler supplies a default one, which in this special
case is:
Object() { }
This constructor executes without effect and returns.
Next, all initializers for the instance variables of class
Point
are executed. As it hap-
pens, the declarations of
x
and
y
do not provide any initialization expressions, so no
action is required for this step of the example. Then the body of the
Point
constructor
is executed, setting
x
to
1
and
y
to
1
.
Next, the initializers for the instance variables of class
ColoredPoint
are executed. This
step assigns the value
0xFF00FF
to
color
. Finally, the rest of the body of the
ColoredPoint
constructor is executed (the part after the invocation of
super
); there happen to be no
statements in the rest of the body, so no further action is required and initialization is
complete.
Example 12.5-2. Dynamic Dispatch During Instance Creation
class Super {
Super() { printThree(); }
void printThree() { System.out.println("three"); }
}
class Test extends Super {
int three = (int)Math.PI; // That is, 3
void printThree() { System.out.println(three); }
public static void main(String[] args) {
Test t = new Test();
t.printThree();
}
}
This program produces the output:
0
3
