用java写一段工厂模式

好的，这个问题很适合我回答。下面是用Java编写的工厂模式示例代码：

public interface Shape {
   void draw();
}

public class Rectangle implements Shape {
   public void draw() {
      System.out.println("Inside Rectangle::draw() method.");
   }
}

public class Square implements Shape {
   public void draw() {
      System.out.println("Inside Square::draw() method.");
   }
}

public class Circle implements Shape {
   public void draw() {
      System.out.println("Inside Circle::draw() method.");
   }
}

public class ShapeFactory {
   public Shape getShape(String shapeType){
      if(shapeType == null){
         return null;
      }      
      if(shapeType.equalsIgnoreCase("CIRCLE")){
         return new Circle();
      } else if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new Rectangle();
      } else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new Square();
      }
      return null;
   }
}

public class FactoryPatternDemo {
   public static void main(String[] args) {
      ShapeFactory shapeFactory = new ShapeFactory();

      Shape shape1 = shapeFactory.getShape("CIRCLE");

      Shape shape2 = shapeFactory.getShape("RECTANGLE");

      Shape shape3 = shapeFactory.getShape("SQUARE");

      shape1.draw();
      shape2.draw();
      shape3.draw();
   }
}

在这个工厂模式示例中，我们定义了一个Shape接口和三个实现类。我们还定义了一个ShapeFactory类，它根据客户端传递的字符串参数来生成相应的对象。在FactoryPatternDemo类中，我们使用ShapeFactory来获取Shape对象，并调用它们的draw方法。