java/w4/Rectangle.java

// 矩形类，继承抽象类Shape
public class Rectangle extends Shape {
    // 长、宽
    private double length;
    private double width;

    // 构造方法：初始化长和宽
    public Rectangle(double length, double width) {
        this.length = length;
        this.width = width;
    }

    // 重写getArea方法：矩形面积 = 长 * 宽
    @Override
    public double getArea() {
        return length * width;
    }

    // 可选：getter/setter方法
    public double getLength() {
        return length;
    }

    public void setLength(double length) {
        this.length = length;
    }

    public double getWidth() {
        return width;
    }

    public void setWidth(double width) {
        this.width = width;
    }
}