Factory manufactures objects

In this pattern, there is a factory and other objects. The factory provides you with the object that you require.

Note: If the factory contains sub-factories, then that is known as an abstract design pattern.

Example: There is a shape factory that gives all the geometrical shapes. The important thing to note is all the shapes implement an interface called Shape.

public class ShapeFactory {
    Shape getShape(String input){
        input = input.toLowerCase();
        switch (input) {
            case "circle":
                return new Circle();
            case "rectangle":
                return new Rectangle();
            default:
                return null;
        }
    }
}

public interface Shape {
    public void draw();
}

public class Rectangle implements Shape{
    @Override
    public void draw() {
        System.out.println("Draw the circle");
    }
}
public class Circle implements Shape{
    @Override
    public void draw() {
        System.out.println("Draw the circle");
    }
}

Usage:

public class MainClass {
    public static void main(String[] args) {
        ShapeFactory factory = new ShapeFactory();
        Shape circle = factory.getShape("Circle");
        circle.draw();
    }
}

Conclusion: A factory should manufacture products that belong to one family.