简单工厂模式

Shape.java

public interface Shape {
    void draw();
}

Circle.java

public class Circle implements Shape{
    @Override
    public void draw() {
        System.out.println("i'm a circle");
    }
}

Rectangle.java

public class Rectangle implements Shape{
    @Override
    public void draw() {
        System.out.println("i'm a rectangle");
    }
}

工厂类ShapeFactory.java

public class ShapeFactory {
    public static Shape getShape(String name) {
        if ("circle".equals(name)) {
            return new Circle();
        }
        if ("rectangle".equals(name)) {
            return new Rectangle();
        }
        return null;
    }
}