Factory Design Pattern

An Alien Factory

import java.util.Random;

public class AlienFactory {

private enum Types { SquidAlien, MonkeyAlien, TigerAlien, RatAlien };

Alien alien = null;

int howManyTypes = Types.values().length;

int randomIndex = (int)(Math.random()*howManyTypes);

Types t = Types.values()[randomIndex]; // back to enum

switch (t) {

case SquidAlien:

alien = new SquidAlien();

break;

case MonkeyAlien:

alien = new MonkeyAlien();

break;

case TigerAlien:

alien = new TigerAlien();

break;

case RatAlien:

alien = new RatAlien();

break;

default:

alien = new Alien("Uknown");

break;

}

return alien;

}

public static void main(String [] args) {

AlienFactory af = new AlienFactory();

for (int i=0; i < 10; ++i) {

Alien x = af.getAlien();

System.out.println( x );

}

}

}

A Better Alien Factory

public class BetterAlienFactory

{

private enum Types { SquidAlien, MonkeyAlien, TigerAlien, RatAlien };

private static Random r = new Random();

public Alien getAlien() {

Alien alien = null;

int rand = r.nextInt(Types.values().length);

Types alienType = Types.values()[rand];

// System.out.println("Alien Type = " + alienType);

try {

alien = (Alien)(Class.forName(alienType.toString()).getDeclaredConstructor().newInstance());

} catch (Exception e) {

System.out.println("Unknown class type.");

}

return alien;

}