Java Reference
In-Depth Information
the field
z
in class
H
hides the field
z
in class
G
. The simple names of fields
x
,
y
, and
z
in class
H
refer to the hiding fields,
not inherited fields. Therefore, if you use the simple name
x
in class
H
, it refers to the field
x
declared in class
H
, not in
class
G
. If you want to refer to the field
x
in class
G
from inside class
H
, you need to use the keyword
super
, for example,
super.x
.
In Listing 16-29, the
FHidingSuper
class declares fields
num
and
name
. In Listing 16-30, the
FHidingSub
class
inherits from the
FHidingSuper
class and it inherits the
num
and
name
fields from it. The
print()
method of the
FHidingSub
class prints the values of the
num
and
name
fields. The
print()
method uses simple names of
num
and
name
fields and they refer to the inherited fields from the
FHidingSuper
class. When you run the
FHidingTest
class in
Listing 16-31, the output shows that the
FHidingSub
class really inherits
num
and
name
fields from its superclass.
Listing 16-29.
FHidingSuper Class with Two Protected Instance Fields
// FHidingSuper.java
package com.jdojo.inheritance;
public class FHidingSuper {
protected int num = 100;
protected String name = "John Jacobs";
}
Listing 16-30.
FHidingSub Class, Which Inherits from the FHidingSuper Class and Inherits Fields num and name
// FHidingSub.java
package com.jdojo.inheritance;
public class FHidingSub extends FHidingSuper {
public void print() {
System.out.println("num: " + num);
System.out.println("name: " + name);
}
}
Listing 16-31.
A Test Class to Demonstrate field's Inheritances
// FHidingTest.java
package com.jdojo.inheritance;
public class FHidingTest {
public static void main(String[] args) {
FHidingSub fhSub = new FHidingSub();
fhSub.print();
}
}
num: 100
name: John Jacobs
Let's consider the definition of class
FHidingSub2
listed in Listing 16-32.
