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);
  }
}