java/w4/Rectangle.java

public class Rectangle extends Shape{
    private double length;
    private double width;

    public Rectangle(double length, double width) {
        if (length <= 0 || width <= 0) {
            throw new IllegalArgumentException("长和宽必须大于0");
        }
        this.length = length;
        this.width = width;
    }

    @Override
    public double getArea() {
        return length * width;
    }

    @Override
    public String getShapeName() {
        return "长方形";
    }

    public double getLength() {
        return length;
    }

    public double getWidth() {
        return width;
    }
}