java定义矩形类rectangle并计算矩形的面积及周长

public class Rectangle {
    private double length; // 矩形的长
    private double width; // 矩形的宽

    public Rectangle(double length, double width) {
        this.length = length;
        this.width = width;
    }

    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;
    }

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

    public double getPerimeter() {
        return 2 * (length + width);
    }
}

使用示例：

Rectangle rect = new Rectangle(5.0, 4.0);
System.out.println("矩形的面积为：" + rect.getArea()); // 输出：矩形的面积为：20.0
System.out.println("矩形的周长为：" + rect.getPerimeter()); // 输出：矩形的周长为：18.0