使用Java 8中的Lambda表达式实现工厂模式

public interface Shape {
 void draw();
}

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

public class ShapeFactory {
 //use getShape method to get object of type shape 
 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();   
  }  
  return null;
 }
}

public class FactoryPatternDemo {
 public static void main(String[] args) {
  ShapeFactory shapeFactory = new ShapeFactory();
  //get an object of Circle and call its draw method.
  Shape shape1 = shapeFactory.getShape("CIRCLE");
  //call draw method of Circle
  shape1.draw();
  //get an object of Rectangle and call its draw method.
  Shape shape2 = shapeFactory.getShape("RECTANGLE");
  //call draw method of Rectangle
  shape2.draw();
 }
}

Inside Circle::draw() method.
Inside Rectangle::draw() method.

Supplier circleSupplier = Circle::new;
Circle circle = circleSupplier.get();

final static Map<String, Supplier> map = new HashMap<>();
 static {
 map.put("CIRCLE", Circle::new);
 map.put("RECTANGLE", Rectangle::new);
 }

public class ShapeFactory {
 final static Map<String, Supplier> map = new HashMap<>();
 static {
 map.put("CIRCLE", Circle::new);
 map.put("RECTANGLE", Rectangle::new);
 } 
 public Shape getShape(String shapeType){
  Supplier shape = map.get(shapeType.toUpperCase());
  if(shape != null) {
  return shape.get();
  }
  throw new IllegalArgumentException("No such shape " + shapeType.toUpperCase());
 }
}

public class FactoryPatternDemo {
 public static void main(String[] args) {
  Supplier shapeFactory = ShapeFactory::new;
  //call draw method of circle
  shapeFactory.get().getShape("circle").draw();
  //call draw method of Rectangle
  shapeFactory.get().getShape("rectangle").draw();  
 }
}

Inside Circle::draw() method.
Inside Rectangle::draw() method.

() -> new Circe(args)