Entry
Java: Class: Inheritance: Create: Simple: Can you give an example of inheritance?
Sep 30th, 2003 05:58
Knud van Eeden,
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--- Knud van Eeden --- 27 September 2003 - 07:42 pm ------------------
Java: Class: Inheritance: Create: Simple: Can you give an example of
inheritance?
1. In general:
Steps: Overview:
1. -Create a class <yourclassnameparent>:
http://www.faqts.com/knowledge_base/view.phtml/aid/24762/fid/163
2. -Create another class <yourclassnamechild>:
1. To indicate that you want to use inheritance, use the following
notation:
class <yourclassnamechild> extends <yourclassnameparent> {
// do something
// e.g. -add new variables, functions and procedures
//
// and or
//
// -overwrite existing variables, functions
// and procedures of that 'parent' class
};
2. So you indicate that your class is inheriting:
1. first the word 'class'
2. followed by the name of 'child' class
3. followed by the word 'extends'
4. followed by the name of the 'parent' class
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2. In specific:
1. -Create a parent class 'addressC',
and give the code for the procedures or functions used in
that class:
class addressC {
//
protected String nameS;
protected String streetS;
protected String cityS;
protected String countryS;
protected String telephoneS;
protected String emailS;
//
// a 'getter' for the 'parent' class
public void PROCView() {
System.out.println( nameS + ' ' + '-' + ' ' + streetS + ' '
+ '-' + ' ' + cityS + ' ' + '-' + ' ' + countryS + ' ' + '-' + ' ' +
telephoneS + ' ' + '-' + ' ' + emailS );
};
// the 'constructor' for the 'parent' class
public addressC( String nameS, String streetS, String cityS,
String countryS, String telephoneS, String emailS ) {
this.nameS = nameS;
this.streetS = streetS;
this.cityS = cityS;
this.countryS = countryS;
this.telephoneS = telephoneS;
this.emailS = emailS;
};
// the 'destructor' for the 'parent' class
protected void finalize() {
};
};
http://www.faqts.com/knowledge_base/view.phtml/aid/16104
2. -Create another child class 'addresscompanyC',
and give the code for the procedures or functions used in
that class:
class addresscompanyC extends addressC {
//
private String companynameS;
//
// a 'getter' for the 'child' class
public void PROCView() {
System.out.println( nameS + ' ' + '-' + ' ' + streetS + ' '
+ '-' + ' ' + cityS + ' ' + '-' + ' ' + countryS + ' ' + '-' + ' ' +
telephoneS + ' ' + '-' + ' ' + emailS + ' ' + '-' + ' ' +
companynameS );
};
// the 'constructor' for the 'child' class (which calls
the 'constructor' of the 'parent' class first, this must be the first
line)
public addresscompanyC( String nameS, String streetS, String
cityS, String countryS, String telephoneS, String emailS, String
companynameS ) {
super( nameS, streetS, cityS, countryS, telephoneS, emailS );
this.companynameS = companynameS;
};
//
// the 'destructor' for the 'child' class
protected void finalize() {
super.finalize();
};
};
4. -Declare the variables which you intend to use with your class:
addressC knudO = new addressC( "myname", "mystreet
1", "mycity", "mycountry", "01-2345678", "myemail@address" );
addressC vanessaO = new addressC( "anothername", "anotherstreet
1", "anothercity", "anothercountry", "01-
3456789", "anotheremail@address" );
addresscompanyC knudcompanyO = new addresscompanyC
( "myname", "mystreet 1", "mycity", "mycountry", "01-
2345678", "myemail@address", "thecompany1name" );
addresscompanyC vanessacompanyO = new addresscompanyC
( "anothername", "anotherstreet
1", "anothercity", "anothercountry", "01-
3456789", "anotheremail@address", "thecompany2name" );
5. -Supply some source code where you use your class
(create another class, which contains the 'main()'
method. Then save this file with the same name
as that class (e.g. 'testinheritanceC.java')
class testinheritanceC {
public static void main( String args[] ) {
//
// initialize variables representing that 'parent' class:
//
addressC knudO = new addressC( "myname", "mystreet
1", "mycity", "mycountry", "01-2345678", "myemail@address" );
addressC vanessaO = new addressC
( "anothername", "anotherstreet
1", "anothercity", "anothercountry", "01-
3456789", "anotheremail@address" );
//
// initialize variables representing that 'child' class:
//
addresscompanyC knudcompanyO = new addresscompanyC
( "myname", "mystreet 1", "mycity", "mycountry", "01-
2345678", "myemail@address", "thecompany1name" );
addresscompanyC vanessacompanyO = new addresscompanyC
( "anothername", "anotherstreet
1", "anothercity", "anothercountry", "01-
3456789", "anotheremail@address", "thecompany2name" );
//
// do something
//
//
// view variables stored in the variables representing
that 'parent' class:
//
knudO.PROCView();
vanessaO.PROCView();
//
// view variables stored in the variables representing
that 'child' class:
//
knudcompanyO.PROCView();
vanessacompanyO.PROCView();
//
// finally release the memory used by that variable, after
use, when you do not need it anymore
}
}
6. -This gives alltogether the following source code:
// save as 'testinheritanceC.java'
// --- 1. declaration of the 'parent' class --- //
class addressC {
//
// it must be 'protected', because
// the 'child' class must be able to read their values
//
protected String nameS;
protected String streetS;
protected String cityS;
protected String countryS;
protected String telephoneS;
protected String emailS;
//
// --- 1.1 functions and procedures of the 'parent' class --- //
//
// 1.1.1 a 'getter' for the 'parent' class
public void PROCView() {
System.out.println( nameS + ' ' + '-' + ' ' + streetS + ' '
+ '-' + ' ' + cityS + ' ' + '-' + ' ' + countryS + ' ' + '-' + ' ' +
telephoneS + ' ' + '-' + ' ' + emailS );
};
//
// 1.1.2 the 'constructor' for the 'parent' class
public addressC( String nameS, String streetS, String cityS,
String countryS, String telephoneS, String emailS ) {
this.nameS = nameS;
this.streetS = streetS;
this.cityS = cityS;
this.countryS = countryS;
this.telephoneS = telephoneS;
this.emailS = emailS;
};
//
// 1.1.3 the 'destructor' for the 'parent' class
protected void finalize() {
};
};
// --- 2. declaration of the 'child' class --- //
class addresscompanyC extends addressC {
//
private String companynameS;
//
// --- 2.1 functions and procedures of the 'child' class --- //
//
// 2.1.1 a 'getter' for the 'child' class
public void PROCView() {
System.out.println( nameS + ' ' + '-' + ' ' + streetS + ' '
+ '-' + ' ' + cityS + ' ' + '-' + ' ' + countryS + ' ' + '-' + ' ' +
telephoneS + ' ' + '-' + ' ' + emailS + ' ' + '-' + ' ' +
companynameS );
};
//
// 2.1.2 the 'constructor' for the 'child' class (which calls
the 'constructor' of the 'parent' class first, this must be the first
line)
public addresscompanyC( String nameS, String streetS, String
cityS, String countryS, String telephoneS, String emailS, String
companynameS ) {
super( nameS, streetS, cityS, countryS, telephoneS, emailS );
this.companynameS = companynameS;
};
//
// 2.1.3 the 'destructor' for the 'child' class
protected void finalize() {
super.finalize();
};
};
// --- 3. do something --- //
class testinheritanceC {
public static void main( String args[] ) {
//
// 3.1 create and initialize variables representing
that 'parent' class:
//
addressC knudO = new addressC( "myname", "mystreet
1", "mycity", "mycountry", "01-2345678", "myemail@address" );
addressC vanessaO = new addressC
( "anothername", "anotherstreet
1", "anothercity", "anothercountry", "01-
3456789", "anotheremail@address" );
//
// 3.2 create initialize variables representing that 'child'
class:
//
addresscompanyC knudcompanyO = new addresscompanyC
( "myname", "mystreet 1", "mycity", "mycountry", "01-
2345678", "myemail@address", "thecompany1name" );
addresscompanyC vanessacompanyO = new addresscompanyC
( "anothername", "anotherstreet
1", "anothercity", "anothercountry", "01-
3456789", "anotheremail@address", "thecompany2name" );
//
// 3.3 do something
//
// 3.3.1 view variables stored in the variables representing
that 'parent' class:
//
knudO.PROCView();
vanessaO.PROCView();
//
// 3.3.2 view variables stored in the variables representing
that 'child' class:
//
knudcompanyO.PROCView();
vanessacompanyO.PROCView();
//
// finally the memory used by that variable will be released
(by Java), after use, when you do not need it anymore
}
}
7. -When you run this source code, you will see e.g. a text screen
with the following information:
> javac.exe c:\temp\testinheritanceC.java
> java testinheritanceC
myname - mystreet 1 - mycity - mycountry - 01-2345678 - myemail@address
anothername - anotherstreet 1 - anothercity - anothercountry -
01-3456789 - anotheremail@address
myname - mystreet 1 - mycity - mycountry - 01-2345678 - myemail@address
- thecompany1name
anothername - anotherstreet 1 - anothercity - anothercountry -
01-3456789 - anotheremail@address - thecompany2name
Press any key to continue . . .
---
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Note: this source code has been tested and worked OK
[kn, ni, mo, 29-09-2003 18:28:33]
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Internet: see also:
C#: Class: Inheritance: Create: Simple: Can you give an example of
inheritance?
http://www.faqts.com/knowledge_base/view.phtml/aid/24889/fid/791
C++: Class: Inheritance: Create: Simple: Can you give an example of
inheritance?
http://www.faqts.com/knowledge_base/view.phtml/aid/24882/fid/163
Delphi: Class: Inheritance: Create: Simple: Can you give an example of
inheritance?
http://www.faqts.com/knowledge_base/view.phtml/aid/24880/fid/175
Java: Class: Inheritance: What is inheritance?
http://www.faqts.com/knowledge_base/view.phtml/aid/24864
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