FactoryPattern.java

package designPatternsAndPrinciples;

/**
 * 
 * @author chengfeili 
 * Jun 5, 2017 10:21:53 PM
 *
 *         The factory pattern, sometimes referred to as the factory method
 *         pattern, is a creational pattern based on the idea of using a factory
 *         class to produce instances of objects based on a set of input
 *         parameters. It is similar to the builder pattern, although it is
 *         focused on supporting class polymorphism.
 */

abstract class Food {
	private int quantity;

	public Food(int quantity) {
		this.quantity = quantity;
	}

	public int getQuantity() {
		return quantity;
	}

	public abstract void consumed();
}

class Hay extends Food {
	public Hay(int quantity) {
		super(quantity);
	}

	public void consumed() {
		System.out.println("Hay eaten: " + getQuantity());
	}
}

class Pellets extends Food {
	public Pellets(int quantity) {
		super(quantity);
	}

	public void consumed() {
		System.out.println("Pellets eaten: " + getQuantity());
	}
}

class Fish extends Food {
	public Fish(int quantity) {
		super(quantity);
	}

	public void consumed() {
		System.out.println("Fish eaten: " + getQuantity());
	}
}

public class FactoryPattern {
	public static Food getFood(String animalName) {
		switch (animalName) {
		case "zebra":
			return new Hay(100);
		case "rabbit":
			return new Pellets(5);
		case "goat":
			return new Pellets(30);
		case "polar bear":
			return new Fish(10);
		}
		// Good practice to throw an exception if no matching subclass could be
		// found
		throw new UnsupportedOperationException("Unsupported animal: " + animalName);
	}
}

class ZooKeeper {
	public static void main(String[] args) {
		final Food food = FactoryPattern.getFood("polar bear");
		food.consumed();
	}
}