当具体对象采用不同的构造函数参数时，在Java中为工厂

Question

我正在尝试在Java中实现Factory模式。我有一个名为Shape的类，该类由Circle和Triangle扩展。问题在于Shape构造函数仅获取2个参数，而Circle则获取3个参数，Triangle也是如此（由于与Circle相同，因此我不会在代码部分中显示）。为了更好地演示它：

    private interface ShapeFactory{
        public Shape create(int x, int y);
    }

    private class CircleFactory implements ShapeFactory{
        public Shape create(float radius, int x, int y){ //error
            return new Circle(radius, x,y);
        }
    }

任何想法如何克服这个问题？我一定不能从工厂内部接收用户的输入（必须从外部接收）。

谢谢！

Answer 1

您有两种选择：

1）抽象工厂：

RectangularShape extends Shape

RoundShape extends Shape

并RectangularShapeFactory与RoundShapeFactory

2）构建器（另请参见有效Java中的第2项）

public Shape {
    private final int x;
    private final int y;
    private final double radius;

    private Shape(Builder builder) {
        x = builder.x;
        y = builder.y;
        radius = builder.radius;
    }

    public static class Builder {
        private final int x;
        private final int y;
        private double radius;

        public Builder(int x, int y) {
            this.x = x;
            this.y = y;
        }

        public Builder radius(double radius) {
            this.radius = radius;
            return this;
        }

        public Shape build() {
            return new Shape(this);
        }    
    }
}

//in client code

    Shape rectangle = new Shape.Builder(x,y).build();
    Shape circle = new Shape.Builder(x,y).radius(radiusValue).build();