java - Do anyone know how to sort stack using array.sort()? I just want to print the ordered list of points by their x coordinates. Any idea? -

import java.util.*;  public class point2d {   private double x;   private double y;    public point2d(double x, double y)   {     this.x = x;     this.y = y;   }    private double euclidean()   {     double distance = math.sqrt((x * x) + (y * y));     return distance;   }    public string tostring()   {     return "x: " + x + ", y: " + y;   }    public static class yorder implements comparator<point2d>   {         public int compare(point2d self, point2d other)     {       if (self.y > other.y)         return 1;        if (self.y < other.y)         return -1;        else         return 0;     }   }    public static void main(string[] args)   {     stack<point2d> stack = new stack<point2d>();      while (!stdin.isempty())     {       double x = stdin.readdouble();       double y = stdin.readdouble();       stack.push(new point2d(x,y));     }      arrays.sort(stack);   } } 

this class , i'm not allowed use collections or arraylist.

arrays.sort(stack); 

should be

 collections.sort(stack, new yorder());//pass comparator