JavaFX 類 Point2D用法及代碼示例

Point2D類是JavaFX的一部分。此類定義空間中的二維點。 Point2D類通過其x，y坐標表示2D點。它繼承了java.lang.Object類。

該類的構造函數：

• Point2D(double x, double y)：創建具有指定x和y坐標的point2D對象。

常用方法：

方法	說明
distance(double x1, double y1)	計算此點與點(x1，y1)之間的距離。
distance(Point2D p)	計算該點與點p之間的距離。
equals(java.lang.Object obj)	返回此對象是否等於指定的對象
getX()	返回該點的x坐標
getY()	返回該點的y坐標
hashCode()	返回該點的哈希碼值。

下麵的程序將說明Point2D類的用法：

1. Java程序創建點2D對象並顯示其坐標並找到其距原點的距離：在此程序中，我們通過使用其x，y坐標作為參數來創建一個名為point2d_1的Point2D對象。我們將使用getX()，getY()函數獲得x，y的值，然後顯示它。我們還在計算點到原點的距離。

   // Java program to create a point 2D  
   // object and display its coordinates 
   // and find its distance from origin 
   import javafx.geometry.Point2D; 
     
   public class Point2D_1 { 
     
       // Main Method 
       public static void main(String args[]) 
       { 
     
           // Create a point2D object 
           Point2D point2d_1 = new Point2D(20.0f, 150.0f); 
     
           double x, y; 
     
           // get the coordinates of the point 
           x = point2d_1.getX(); 
           y = point2d_1.getY(); 
     
           // display the coordinates of the point 
           System.out.println("x coordinate = " + x  
                         + ", y coordinate = " + y); 
     
           // print its distance from origin 
           System.out.println("distance from origin = " 
                           + point2d_1.distance(0, 0)); 
       } 
   }

   輸出：

   x coordinate = 20.0, y coordinate = 150.0
   distance from origin = 151.32745950421557
   

2. Java程序創建3個Point2D對象並顯示其坐標和距原點的距離，並檢查3個點中的哪個點相似以及兩個點之間的距離：在此程序中，我們通過傳遞其x，y坐標作為參數來創建3個Point2D對象，它們分別名為point2d_1，point2d_2，point2d_3。我們使用getX()，getY()函數獲得x，y值，然後顯示它。我們還在計算點到原點的距離，並為三個點中的每一個顯示它。我們還使用equals()函數顯示兩個點是否相等，以及使用distance()函數顯示兩個點之間的距離。

   // Java program to create 3 Point2D objects and display 
   // their coordinates and distance from origin and 
   // check which of the 3 points are similar and  
   // their distances between two points 
   import javafx.geometry.Point2D; 
     
   public class Point2D_2 { 
     
       // Main Method 
       public static void main(String args[]) 
       { 
     
           // Create three point2D objects 
           Point2D point2d_1 = new Point2D(120.0f, 50.0f); 
           Point2D point2d_2 = new Point2D(120.0f, 50.0f); 
           Point2D point2d_3 = new Point2D(200.0f, 120.0f); 
     
           // Display the coordinates of the 3 points 
           display(point2d_1); 
           display(point2d_2); 
           display(point2d_3); 
     
           // Check whether any point is equal to other or not 
           System.out.println("Point 1 equals Point 2 = " 
                           + point2d_1.equals(point2d_2)); 
     
           System.out.println("Point 2 equals Point 3 = " 
                           + point2d_2.equals(point2d_3)); 
     
           System.out.println("Point 3 equals Point 1 = " 
                           + point2d_3.equals(point2d_1)); 
     
           // distance between two points 
           System.out.println("Distane between point 1 and point 2 = " 
                                     + point2d_1.distance(point2d_2)); 
     
           System.out.println("Distane between point 2 and point 3 = " 
                                      + point2d_2.distance(point2d_3)); 
     
           System.out.println("Distane between point 3 and point 1 = " 
                                       + point2d_3.distance(point2d_1)); 
       } 
     
       // display method 
       public static void display(Point2D point2d) 
       { 
     
           double x, y; 
     
           // get the coordinates of the point 
           x = point2d.getX(); 
           y = point2d.getY(); 
     
           // display the coordinates of the point 
           System.out.println("x coordinate = " + x  
                         + ", y coordinate = " + y); 
     
           // print its distance from origin 
           System.out.println("Distance from origin = " 
                             + point2d.distance(0, 0)); 
       } 
   }

   輸出：

   x coordinate = 120.0, y coordinate = 50.0
   Distance from origin = 130.0
   x coordinate = 120.0, y coordinate = 50.0
   Distance from origin = 130.0
   x coordinate = 200.0, y coordinate = 120.0
   Distance from origin = 233.23807579381202
   Point 1 equals Point 2 = true
   Point 2 equals Point 3 = false
   Point 3 equals Point 1 = false
   Distane between point 1 and point 2 = 0.0
   Distane between point 2 and point 3 = 106.30145812734649
   Distane between point 3 and point 1 = 106.30145812734649
   

注意：以上程序可能無法在在線IDE中運行。請使用離線編譯器。

參考：https://docs.oracle.com/javafx/2/api/javafx/geometry/Point2D.html