无法访问我的子类中的方法

Question

所以，我非常接近完成一个项目；但是，我正在尝试访问 Circle 和 Rectangle 类中的方法。到目前为止，我的代码是：

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.Scanner;


public class hw2redo 
{
     public static void main(String[] args) throws FileNotFoundException {

          GeometricObject g = null;
          File diskFile = new File("file.txt");
          Scanner diskScanner = new Scanner(diskFile);
          ArrayList<GeometricObject> list = new ArrayList<GeometricObject>();
          while(diskScanner.hasNext()){
              String geolist = diskScanner.nextLine();
              g = recreateObject(geolist);

              list.add(g);

          }
          diskScanner.close();
         /* while (diskScanner.hasNext()) {
              String list = diskScanner.nextLine();
              g = recreateObject(list);
          }
          diskScanner.close();*/
          showObjects(list);
       }





    private static GeometricObject recreateObject(String data) {

          String[] list = data.split(",");
          String geoObject = list[0];

          if (geoObject.equals("Circle")) {
             String color = list[1];
             boolean filled = Boolean.valueOf(list[2]); 
             double radius = Double.valueOf(list[3]);
             return new Circle(radius, color, filled);
          }

          if (geoObject.equals("Rectangle")) {
             String color = list[1];
             boolean filled = Boolean.valueOf(list[2]);
             double height = Double.valueOf(list[3]);
             double width = Double.valueOf(list[4]);
             return new Rectangle(width, height, color, filled);
          }
        return null;


       }
     private static void showObjects(ArrayList<GeometricObject> list)
     {
         for(GeometricObject o : list)
            {

                 if(o.equals("Circle"))
                     printCircle();

            }
     }
    }

class GeometricObject {
       private String color = "white";
       private boolean filled;
       private java.util.Date dateCreated;
       private String data;

      /** Construct a default geometric object */
      public GeometricObject() {
     dateCreated = new java.util.Date();
     //this.data = data;
      }

     /** Construct a geometric object with the specified color
     * and filled value */
     public GeometricObject(String color, boolean filled) {
     dateCreated = new java.util.Date();
     this.color = color;
     this.filled = filled;
     }

     /** Return color */
     public String getColor() {
     return color;
     }

     /** Set a new color */
     public void setColor(String color) {
     this.color = color;
     }

     /** Return filled. Since filled is boolean,
     its getter method is named isFilled */
     public boolean isFilled() {
     return filled;
     }

     /** Set a new filled */
     public void setFilled(boolean filled) {
     this.filled = filled;
     }

     /** Get dateCreated */
     public java.util.Date getDateCreated() {
     return dateCreated;
     }

     /** Return a string representation of this object */
     public String toString() {
     return "created on " + dateCreated + "\ncolor: " + color +
     " and filled: " + filled;
     }
     }

class Circle extends GeometricObject
{
private double radius;

public Circle() {
}

public Circle(double radius) {
this.radius = radius;
}
public Circle(double radius,
String color, boolean filled) {
this.radius = radius;
setColor(color);
setFilled(filled);
}

/** Return radius */
public double getRadius() {
return radius;
}

/** Set a new radius */
public void setRadius(double radius) {
this.radius = radius;
}

/** Return area */
public double getArea() {
return radius * radius * Math.PI;
}

/** Return diameter */
public double getDiameter() {
return 2 * radius;
}

/** Return perimeter */
public double getPerimeter() {
return 2 * radius * Math.PI;
}

/** Print the circle info */
public void printCircle() {
System.out.println("The circle is created " + getDateCreated() +
" and the radius is " + radius);
}
}

class Rectangle extends GeometricObject {
private double width;
private double height;

public Rectangle() {
}

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

public Rectangle(
double width, double height, String color, boolean filled) {
this.width = width;
this.height = height;
setColor(color);
setFilled(filled);
}

/** Return width */
public double getWidth() {
return width;
}

/** Set a new width */
public void setWidth(double width) {
this.width = width;
}

/** Return height */
public double getHeight() {
return height;
}

/** Set a new height */
public void setHeight(double height) {
this.height = height;
}

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

/** Return perimeter */
public double getPerimeter() {
return 2 * (width + height);
}
}

当我尝试访问我的 Circle 子类中的 printCircle 方法时，我收到了错误

没有为类型 hw2redo 定义方法 printCircle()

关于我做错了什么的任何帮助或想法。谢谢！

Answer 1

请注意：printCircle() 是 Circle 类的函数，因此要访问此方法，您需要在对象上调用 printCircle()：

private static void showObjects(ArrayList<GeometricObject> list) {
     for(GeometricObject o : list) {
             if(o.equals("Circle"))
                 (Circle) o.printCircle();
     }
}

试试这个

Answer 2

当您尝试拨打printCircle 时，有一些不同的地方是错误的。主要问题，也是编译器试图告诉您的问题，是您在 hw2redo 类中调用 printCircle。那没有意义；该方法属于Circle 类。这就是我将如何修复您的代码。从你只关心GeometricObject 的事实来看，它是一个圆圈，为什么还要把它作为你的参数呢？将其更改为：

private static void showObjects(ArrayList<Circle> list){
    for(Circle c : list){
        c.printCircle();
    }
}