Java - 根据 X 和 Y 坐标对一组点进行排序

Question

我有一个需要按 X 和 Y 坐标排序的点对象列表，但是当我将它们传递给比较器对象时，只有一个坐标被排序（调用的第一个坐标）。对于为什么会发生这种情况有什么想法吗？

static public List<Point> convertToThreeByThreeGrid(String points) {
    String[] ptsArray;
    List<Point> ptsList = new ArrayList<>();
    String stripString = points.replace("[", "").replace("]", "").replace("(", "").replace(")", "").replace(" ", ",").trim();
    ptsArray = stripString.split(",");

    for(int i = 0; i < ptsArray.length; i += 2) {
        int x = Integer.parseInt(ptsArray[i]);
        int y = Integer.parseInt(ptsArray[i + 1]);
        System.out.println("X: " + x);
        System.out.println("Y: " + y);
        ptsList.add(new Point(x, y));
    }

    Collections.sort(ptsList, new Comparator<Point>() {
        public int compare(Point a, Point b) {
            int result = Integer.compare((int) a.getX(), (int) b.getX());
            if (result == 0 ) {
                result = Integer.compare((int) a.getY(), (int) b.getY());
            }
            return result;
        }
    });

   // subtract each coordinate by smallest x and y coordinate values
    List<Point> convertedPtList = new ArrayList<>();
    int smallestX = (int) ptsList.get(0).getX();
    int smallestY = (int) ptsList.get(0).getY();
    for (int i = 1; i < ptsList.size(); i++) {
        int x = ((int) ptsList.get(i).getX() - smallestX);
        int y = ((int) ptsList.get(i).getY() - smallestY);
        convertedPtList.add(new Point(x, y));
    }
    return convertedPtList;

  }
}

输出：

[java.awt.Point[x=10,y=26], java.awt.Point[x=10,y=26], java.awt.Point[x=10,y=28], java.awt.点[x=12,y=26]]

[java.awt.Point[x=13,y=26], java.awt.Point[x=13,y=28], java.awt.Point[x=13,y=28], java.awt.点[x=14,y=27], java.awt.Point[x=14,y=27], java.awt.Point[x=15,y=26], java.awt.Point[x=15] ,y=28],java.awt.Point[x=15,y=28]]

[java.awt.Point[x=16,y=26], java.awt.Point[x=16,y=28], java.awt.Point[x=16,y=28], java.awt.点[x=18,y=26], java.awt.Point[x=18,y=26], java.awt.Point[x=18,y=28]]

Answer 1

for(int i = 0; i < ptsArray.length; i += 2) {
    int x = Integer.parseInt(ptsArray[i]);
    int y = Integer.parseInt(ptsArray[i+1]);
    ptsList.add(new Point(x, y));
}

Collections.sort( ptsList, new Comparator<Point>() {
       public int compare(Point x1, Point x2) {
         int result = Double.compare(x1.getX(), x2.getX());
         if ( result == 0 ) {
           // both X are equal -> compare Y too
           result = Double.compare(x1.getY(), x2.getY());
         } 
         return result;
      }
    });

// ptsList is now sorted by both X and Y!

编辑：

要找到最低的 X 和最低的 Y，您也可以采用“经典”方式，无需任何（双重）排序：

int minX = Integer.MAX_VALUE;
int minY = Integer.MAX_VALUE;

for ( Point p : ptsList ) {

  final int x = (int)p.getX();
  final int y = (int)p.getY();

  if ( x < minX ) {
    minX = x;
  } 

  if ( y < minY ) {
    minY = y;
  }
}