Question

由于java无法找到我放置的变量的问题，我一直遇到此任务的问题。作业是：实现具有以下属性的Rectangle类。

在构造函数中指定Rectangle对象，矩形的左右边缘位于x和x + width处。顶部和底部边缘位于y和y +高度。

方法getPerimeter计算并返回Rectangle的周长。

方法getArea计算并返回Rectangle的区域。

方法绘制显示Rectangle对象的新实例。有关DrawingTool方法的详细信息，请参阅DrawingTool API。

使用默认构造函数和可以获取x和y坐标，矩形长度和宽度的构造函数来尝试矩形。以下是一些示例构造函数调用：

Rectangle rectA = new Rectangle（）;

Rectangle rectB = new Rectangle（0，-80,400,160）;

Rectangle rectC = new Rectangle（100，-100,20,300）;

这是我的作业驱动程序：

public class Driver_class
{
public static void main(String[] args) {
        P4_Icel_Murad_Rectangle rectA = new P4_Icel_Murad_Rectangle();
        P4_Icel_Murad_Rectangle rectB = new P4_Icel_Murad_Rectangle(0,-80,400,160);
        P4_Icel_Murad_Rectangle rectC = new P4_Icel_Murad_Rectangle(100,-100,20,300);

}
}

和我的主要（）

public class P4_Icel_Murad_Rectangle
{

    /**
     * Constructor for objects of class P4_Icel_Murad
     */
    public P4_Icel_Murad_Rectangle(double x, double y, double width, double height)
    {
        // initialise instance variables

        DrawingTool Pen;
        SketchPad Paper;
        //new sketchpad
        Paper = new SketchPad(500,500);
        Pen = new DrawingTool(Paper);
        getPerimeter();
        getArea();
        draw();        
    }
   //Constructor # 2
   public P4_Icel_Murad_Rectangle()
   {
       double x = 0;
         double y = 0;
         double width = 0;
         double height = 0;
       DrawingTool Pen;
        SketchPad Paper;
        //new sketchpad
        Paper = new SketchPad(500,500);
        Pen = new DrawingTool(Paper);
        getPerimeter();
        getArea();
        draw();
    }
public double getPerimeter(){
     double per = (width * 2) + height * 2;
    return per;
}
public double getArea(){
    double area = width * height;
    return area;
}
public void draw(){
 pen.down();
 pen.turnRight(90);
 pen.forward(x);
 pen.turnLeft(90);
 pen.forward(width);
 pen.turnLeft(90);
 pen.forward(height);
 pen.turnLeft();
 pen.forward(y);

}
}

Java说它无法找到变量宽度，尽管我已经列出了它。感谢您的帮助！

Answer 1

您的变量仅在构造函数的范围内声明。在课堂上让他们private。

Answer 2

public static class P4_Icel_Murad_Rectangle {

    SketchPad Paper = new SketchPad(500, 500);
    DrawingTool pen = new DrawingTool(Paper);

    double x = 0;
    double y = 0;
    double width = 0;
    double height = 0;

    /**
     * Constructor for objects of class P4_Icel_Murad
     */
    public P4_Icel_Murad_Rectangle(double x, double y, double width, double height) {
        // initialise instance variables

        getPerimeter();
        getArea();
        draw();
    }

    // Constructor # 2
    public P4_Icel_Murad_Rectangle() {
        getPerimeter();
        getArea();
        draw();
    }

    public double getPerimeter() {
        double per = (width * 2) + height * 2;
        return per;
    }

    public double getArea() {
        double area = width * height;
        return area;
    }

    public void draw() {
        pen.down();
        pen.turnRight(90);
        pen.forward(x);
        pen.turnLeft(90);
        pen.forward(width);
        pen.turnLeft(90);
        pen.forward(height);
        pen.turnLeft();
        pen.forward(y);

    }
}

Java无法找到变量Rectangle Draw / find Area / find Perimeter

2 个答案: