Welcome to Abstract Factory Design Pattern in java example. Abstract Factory design pattern is one of the Creational patterns. Abstract Factory pattern is almost similar to Factory Pattern except the fact that its more like factory of factories.
If you are familiar with factory design pattern in java, you will notice that we have a single Factory class. This factory class returns different subclasses based on the input provided and factory class uses if-else or switch statement to achieve this. In the Abstract Factory pattern, we get rid of if-else block and have a factory class for each sub-class. Then an Abstract Factory class that will return the sub-class based on the input factory class. At first, it seems confusing but once you see the implementation, it’s really easy to grasp and understand the minor difference between Factory and Abstract Factory pattern. Like our factory pattern post, we will use the same superclass and sub-classes.
Computer.java
package com.journaldev.design.model;
public abstract class Computer {
public abstract String getRAM();
public abstract String getHDD();
public abstract String getCPU();
@Override
public String toString(){
return "RAM= "+this.getRAM()+", HDD="+this.getHDD()+", CPU="+this.getCPU();
}
}
PC.java
package com.journaldev.design.model;
public class PC extends Computer {
private String ram;
private String hdd;
private String cpu;
public PC(String ram, String hdd, String cpu){
this.ram=ram;
this.hdd=hdd;
this.cpu=cpu;
}
@Override
public String getRAM() {
return this.ram;
}
@Override
public String getHDD() {
return this.hdd;
}
@Override
public String getCPU() {
return this.cpu;
}
}
Server.java
package com.journaldev.design.model;
public class Server extends Computer {
private String ram;
private String hdd;
private String cpu;
public Server(String ram, String hdd, String cpu){
this.ram=ram;
this.hdd=hdd;
this.cpu=cpu;
}
@Override
public String getRAM() {
return this.ram;
}
@Override
public String getHDD() {
return this.hdd;
}
@Override
public String getCPU() {
return this.cpu;
}
}
First of all we need to create a Abstract Factory interface or abstract class. ComputerAbstractFactory.java
package com.journaldev.design.abstractfactory;
import com.journaldev.design.model.Computer;
public interface ComputerAbstractFactory {
public Computer createComputer();
}
Notice that createComputer()
method is returning an instance of super class Computer
. Now our factory classes will implement this interface and return their respective sub-class. PCFactory.java
package com.journaldev.design.abstractfactory;
import com.journaldev.design.model.Computer;
import com.journaldev.design.model.PC;
public class PCFactory implements ComputerAbstractFactory {
private String ram;
private String hdd;
private String cpu;
public PCFactory(String ram, String hdd, String cpu){
this.ram=ram;
this.hdd=hdd;
this.cpu=cpu;
}
@Override
public Computer createComputer() {
return new PC(ram,hdd,cpu);
}
}
Similarly we will have a factory class for Server
subclass. ServerFactory.java
package com.journaldev.design.abstractfactory;
import com.journaldev.design.model.Computer;
import com.journaldev.design.model.Server;
public class ServerFactory implements ComputerAbstractFactory {
private String ram;
private String hdd;
private String cpu;
public ServerFactory(String ram, String hdd, String cpu){
this.ram=ram;
this.hdd=hdd;
this.cpu=cpu;
}
@Override
public Computer createComputer() {
return new Server(ram,hdd,cpu);
}
}
Now we will create a consumer class that will provide the entry point for the client classes to create sub-classes. ComputerFactory.java
package com.journaldev.design.abstractfactory;
import com.journaldev.design.model.Computer;
public class ComputerFactory {
public static Computer getComputer(ComputerAbstractFactory factory){
return factory.createComputer();
}
}
Notice that its a simple class and getComputer
method is accepting ComputerAbstractFactory
argument and returning Computer
object. At this point the implementation must be getting clear. Let’s write a simple test method and see how to use the abstract factory to get the instance of sub-classes. TestDesignPatterns.java
package com.journaldev.design.test;
import com.journaldev.design.abstractfactory.PCFactory;
import com.journaldev.design.abstractfactory.ServerFactory;
import com.journaldev.design.factory.ComputerFactory;
import com.journaldev.design.model.Computer;
public class TestDesignPatterns {
public static void main(String[] args) {
testAbstractFactory();
}
private static void testAbstractFactory() {
Computer pc = com.journaldev.design.abstractfactory.ComputerFactory.getComputer(new PCFactory("2 GB","500 GB","2.4 GHz"));
Computer server = com.journaldev.design.abstractfactory.ComputerFactory.getComputer(new ServerFactory("16 GB","1 TB","2.9 GHz"));
System.out.println("AbstractFactory PC Config::"+pc);
System.out.println("AbstractFactory Server Config::"+server);
}
}
Output of the above program will be:
AbstractFactory PC Config::RAM= 2 GB, HDD=500 GB, CPU=2.4 GHz
AbstractFactory Server Config::RAM= 16 GB, HDD=1 TB, CPU=2.9 GHz
Here is the class diagram of abstract factory design pattern implementation.
I recently uploaded a video on YouTube for abstract factory design pattern. In the video, I discuss when and how to implement an abstract factory pattern. I have also discussed what is the difference between the factory pattern and abstract factory design pattern. https://youtu.be/BPkYkyVWOaw
You can download the examples code from my GitHub Project.
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Hi, I just want to provide a constructive criticism about the example. Actually, this is an example of Factory Method implementations.
- Gabriel Armburu
I would suggest to have one factory for computer and other factory for some other component and have an abstract factory as a whole for computer factory and some other factory., that way you will create abstract factory of factories and thus computer will become an interface with multiple computer implementations and the other factory with the same way. having a factory for every single concrete implementation of computer is not a good idea and it will not be a good example to project abstract factory.
- vish
If the concrete classes ‘PC’ & ‘Server’ have the same set of properties as the abstract class ‘Computer’, why not to have these properties defined in the ‘Computer’ class instead, along with the corresponding getters?
- Vikram Sherigar
Can you please explain more on Abstraction in case of Factory as well as Abstract Factory. I am not able to see the abstraction as the client still needs to know what to instantiate and what parameters to pass to instantiate the required class.
- Suhas Nayak
Your blog is very helpful :) Thanks!
- AJ
We can have some better example of abstract factory, need to improve AbastractFactory class
- Umesh
Hello, There is a small typo - “Banefits” Regards, Andrii
- Andrii
If in the end the user has to write new PCFactory() and new ServerFactory() then what is the use of creating all those interfaces. means instead of PCFactory and ServerFactory he could use new PC() and new Server()
- Ashish Doneriya
good
- abc
Your article and your example is very good and useful. I used some your example on my blog: https://stackjava.com and I place back link to your page. Because my students can not read english language… Please let me know if you feel bothered I will remove it. Thanks!
- kai