Factory Method Pattern

Overview

Factory method is a creational pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.

Advantages

• Avoid coupling between creator and concrete products.
• Satisfies single responsiblity principle as creation logic is separated with core logic.
• Satsifies open closed principle as new types of products can be introduced without breaking existing client code.

Applicability

• When you don’t know beforehand the exact types and dependencies of the objects your code should work with. Factory method allows easy extension of product construction code independently from rest of code.

interface Button {
	public void setLabel(String label);
    public String getLabel();
    
	public void setBgColour(String colour);
    public String getBgColour();

	public void click();
}

// And multiple concrete classes that implement Button...

public class ButtonFactory {
	public static Button getButton() {
		String platform = System.getProperty("os.name");
		return getButton(platform);
	}

	public static Button getButton(String platform) {
		Button btn = null;

		if (platform.equalsIgnoreCase("Html")) {
			btn = new ButtonHtml();
		} else if (platform.equalsIgnoreCase("Windows 10")) {
			btn = new ButtonWin10();
		} else if (platform.equalsIgnoreCase("MacOs")) {
			btn = new ButtonMacOs();
		} else if (platform.equalsIgnoreCase("Linux")) {
			btn = new ButtonLinux();
		} else {
			new Exception("Unknwon platform type!");
		}

		return btn;
	}
}