Java基础之集合框架——使用真的的链表LinkedList<>（TryPolyLine）

控制台程序。

 public class Point {
   // Create a point from its coordinates
   public Point(double xVal, double yVal) {
      x = xVal;
      y = yVal;
   }

   // Create a point from another point
   public Point(Point point) {
      x = point.x;
      y = point.y;
   }

   // Convert a point to a string
   @Override
   public String toString() {
      return x+","+y;
   }

   // Coordinates of the point
   protected double x;
   protected double y;
 }

 import java.util.LinkedList;

 public class PolyLine {
   // Construct a polyline from an array of points
   public PolyLine(Point[] points) {
     // Add the  points
     for(Point point : points) {
       polyline.add(point);
     }
   }
   // Construct a polyline from an array of coordinates
   public PolyLine(double[][] coords) {
     for(double[] xy : coords) {
       addPoint(xy[0], xy[1]);
     }
   }

   // Add a Point object to the list
   public void addPoint(Point point) {
     polyline.add(point);                                               // Add the new point
   }

   // Add a point to the list
   public void addPoint(double x, double y) {
     polyline.add(new Point(x, y));
   }

   // String representation of a polyline
   @Override
   public String toString() {
     StringBuffer str = new StringBuffer("Polyline:");

     for(Point point : polyline) {
       str.append(" "+ point);                                          // Append the current point
     }
     return str.toString();
   }

   private LinkedList<Point> polyline = new LinkedList<>();
 }

 public class TryPolyLine {
   public static void main(String[] args) {
     // Create an array of coordinate pairs
     double[][] coords = { {1, 1}, {1, 2}, { 2, 3},
                           {-3, 5}, {-5, 1}, {0, 0} };

     // Create a polyline from the coordinates and display it
     PolyLine polygon = new PolyLine(coords);
     System.out.println(polygon);
     // Add a point and display the polyline again
     polygon.addPoint(10, 10);
     System.out.println(polygon);

     // Create Point objects from the coordinate array
     Point[] points = new Point[coords.length];
     for(int i = 0; i < points.length; ++i)
     points[i] = new Point(coords[i][0],coords[i][1]);

     // Use the points to create a new polyline and display it
     PolyLine newPoly = new PolyLine(points);
     System.out.println(newPoly);
   }
 }