Java找不到方法

Question

当我尝试在另一个类中使用我成功编译的代码时，它显示错误:在我的 max 和compareTo 方法上找不到符号。

我真的可以使用这个帮助，我对编码基本上是新手，这是我在这里发表的第一篇文章，所以如果我公然违反规则，请原谅我。

public class assignment13_5 {
  public static void main(String[] args){
    TriangleFromSimpleGeometricObject x = new TriangleFromSimpleGeometricObject(4, 4, 4, "blue", true);
    TriangleFromSimpleGeometricObject y = new TriangleFromSimpleGeometricObject(4, 4, 4, "white", false);
    int i = x.compareTo(y);
    //this code is from my text book
    System.out.print(max(i));
  }
}

/**I got the base code from http://www.cs.armstrong.edu/liang/intro9e/html/GeometricObject.html?
then modified it for the comparable method*/

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

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

  /** Construct a geometric object with color and filled value */
  protected 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,
   *  the get 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;
  }

  @Override
  public String toString() {
    return "created on " + dateCreated + "\ncolor: " + color +
      " and filled: " + filled;
  }

  /** Abstract method getArea */
  public abstract double getArea();

  /** Abstract method getPerimeter */
  public abstract double getPerimeter();


public static String max(int x){
    if (x == 1)
      return "The first is bigger.";
    else if (x == -1)
      return "The second is bigger.";
    else
      return "They are equal.";
  }
public abstract class ComparableGeometricObject extends GeometricObject
  implements Comparable<ComparableGeometricObject> {

  //@Override // Implement the compareTo method defined in Comparable
  public abstract int compareTo(GeometricObject o) {
    if (getArea() > o.getArea())
      return 1;
    else if (getArea() < o.getArea())
      return -1;
    else
      return 0;
  }

  @Override // Implement the toString method in GeometricObject
  public String toString() {
    return super.toString() + " Area: " + getArea();
  }
}
  }

public class TriangleFromSimpleGeometricObject extends SimpleGeometricObject {

    private double s1 = 1;
    private double s2 = 1;
    private double s3 = 1;
    private double side;

    public TriangleFromSimpleGeometricObject(){
    }





    public TriangleFromSimpleGeometricObject(double s1, double s2, double s3, String color, boolean filled) throws IllegalTriangleException{

            this.s1 = s1;
            this.s2 = s2;
            this.s3 = s3;
            setColor(color);
            setFilled(filled);

          if (s1 + s2 <= s3){
            if (s1 < s2){
              if (s1 < s3)
                side = s1;
            }
            else if (s2 < s1){
              if (s2 < s3)
                side = s2;
            }
            else
              side = s3;
            throw new IllegalTriangleException("N/A");
          }
        }

        public double getArea(){
          double s = (s1 + s2 + s3) / 2;

          double area = Math.sqrt(s * (s - s1) * ( s - s2) * ( s - s3) );

          return area;
        }

        public double getPerimeter(){
          double perimeter = s1 + s2 + s3;;

          return perimeter;
        }

        public void setSide(int side, int newSide) {
          if (side == 1)
            s1 = newSide;

          if (side == 2)
            s2 = newSide;

          if (side == 3)
            s3 = newSide;
        }

        public void getSide(int side){
          if (side == 1)
            System.out.println("The first side is: " + s1);

          if (side == 2)
            System.out.println("The first side is: " + s2);

          if (side == 3)
            System.out.println("The first side is: " + s3);
        }

        public String toString(){
          return "Triangle: side1 = " + s1 + " side2 = " + s2 + " side3 = " + s3 + " color = " + getColor() + " is filled = " + isFilled();
        }
    }

public class RectangleFromSimpleGeometricObject
  extends SimpleGeometricObject {

  private double width;
  private double height;

  public RectangleFromSimpleGeometricObject() {
  }

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

  public RectangleFromSimpleGeometricObject(
    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);
  }
}

Answer 1

对compareTo()的引用位于TriangleFromSimpleGeometricObject类型的对象上；在该类中需要有一个声明，位于大括号内，例如

public int compareTo(TriangleFromSimpleGeometricObject y) {
  // with code in here
}

方法 max() 显然应该位于您发布的类中，因此其中应该有声明

private static ? max(int i) {  // could also be public, or even protected
   // with code in here
}

(更正为静态)它需要是静态的，因为它是从静态方法调用的，而不引用实例。我们不知道它的返回类型。

这些事情显然不是这样的，因为编译器说它找不到它们。造成这种情况的原因有多种；要知道它们是什么，我们必须查看此类和 TriangleFromSimpleGeometricObject 的所有代码。

--- 已编辑，现在我们有了更多信息

方法max(int)是GeometricObject上的静态方法；为了调用它，您要么必须在方法调用前面加上类名，要么位于该类中。所以改变你的路线

System.out.println(max(i));

到

System.out.println(GeometricObject.max(i));

这应该可以修复那里的编译错误。这能解决所有问题吗？

顺便说一句，max 对于该方法来说是一个特别糟糕的名字(我这么说是在不知道是你还是其他人写的情况下)。它不计算最大值，与最大值没有任何关系，因此它的名称并不反射(reflect)它的作用。但是修复这个问题并不能修复编译错误，即使假设您能够更改它，而且这不是您所要求的。