为什么这个教科书程序不能识别我的 Point2D 对象？

Question

以下程序在我正在关注的教科书中提供。它应该使用 Point2D 类计算两个坐标 (x1, y1) 和 (x2, y2) 之间的距离：

import java.util.Scanner;
import javafx.geometry.Point2D;

public class TestPoint2D {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.print("Enter point1's x-, y-coordinates");
        double x1 = input.nextDouble();
        double y1 = input.nextDouble();
        System.out.print("Enter point2's x-, y coordinates");
        double x2 = input.nextDouble();
        double y2 = input.nextDouble();

        Point2D p1 = new Point2D(x1, y2);
        Point2D p2 = new Point2D(x2, y2);
        System.out.println("p1 is " + p1.toString());
        System.out.println("p2 is " + p2.toString());
        System.out.println("The distance between p1 and p2 is " +
            p1.distance(p2));
    }
}

我已经检查了很多很多次，并确保它被正确复制。当我尝试在终端中编译程序时，我收到以下错误消息：

import javafx.geometry.Point2D;
                      ^
TestPoint2D.java:15: error: cannot find symbol
        Point2D p1 = new Point2D(x1, y2);
        ^
  symbol:   class Point2D
  location: class TestPoint2D
TestPoint2D.java:15: error: cannot find symbol
        Point2D p1 = new Point2D(x1, y2);
                         ^
  symbol:   class Point2D
  location: class TestPoint2D
TestPoint2D.java:16: error: cannot find symbol
        Point2D p2 = new Point2D(x2, y2);
        ^
  symbol:   class Point2D
  location: class TestPoint2D
TestPoint2D.java:16: error: cannot find symbol
        Point2D p2 = new Point2D(x2, y2);
                         ^
  symbol:   class Point2D
  location: class TestPoint2D
5 errors

为什么程序不能识别新的 Point2D 对象？

Answer 1

您缺少的是 JavaFX 运行时 jar 的 jar，请在此处参考此问题 What's the location of the JavaFX runtime JAR file, jfxrt.jar, on Linux?

它详细解释了 jfxrt.jar 在 Java 7 和 8 中的位置。

希望对你有帮助！！