Avoid creation of duplicate vertices in digraph (using jgrapht)

Question

I am looking for a way to avoid creating duplicates in my digraph (I use the jgrapht library).

I read some topics which said to use: directedGraph.setCloneable(false); But it doesn't seem to be right, can't find it in the library's documentation and I get an error on this line saying it doesn't exists.

I created my graph using:

public static DirectedGraph<Point, DefaultEdge> directedGraph = new DefaultDirectedGraph<Point, DefaultEdge>(DefaultEdge.class);

And then it adds vertices to it based on the flood fill algorithm (adds vertices and edges as the algorithm go through every point, below is a part of it):

// Up
    xToFillNext = x-1;
    yToFillNext = y;
    if (xToFillNext==targetX && yToFillNext==targetY && !forbiddenDirection.equals(Direction.UP)) {
      Point myPoint = new Point(x, y);
      Point myNextPoint = new Point(xToFillNext, yToFillNext);

      directedGraph.addVertex(myPoint);
      directedGraph.addVertex(myNextPoint);
      directedGraph.addEdge(myPoint, myNextPoint);
      return true;
    } else if (xToFillNext>=0 && originValue==matrix[xToFillNext][yToFillNext] && !forbiddenDirection.equals(Direction.UP)) {  
      Point myPoint = new Point(x, y);
      Point myNextPoint = new Point(xToFillNext, yToFillNext);

      directedGraph.addVertex(myPoint);
      directedGraph.addVertex(myNextPoint);
      directedGraph.addEdge(myPoint, myNextPoint);   
      fillingReachedTargetPosition = 
        fillReachesTargetPosition(matrix, xToFillNext, yToFillNext, targetX, targetY, fillValue, Direction.DOWN );
      if (fillingReachedTargetPosition) {
        return true;
      }
    }

But when I print the list of vertices, there are duplicates which I either need to get rid of, or avoid them to be created. Is there a way to do it ?

EDIT: I created a Point class:

public static class Point {

  public int x;
  public int y;

  public  Point(int x, int y) 
  {

    this.x = x;
    this.y = y;
  }
  @Override
    public String toString() {
    return ("[x="+x+" y="+y+"]");
  }
}

Answer 1

In order to detect duplicate vertices you need to supply also method for equals and hashCode. Ohterwise JVM does not know, how to compare the objects, and uses object id (==) which would not identify two different object of class Point as duplicate or equal.

e.g. ( The hashCode has countless number of possible implementations)

@Override
public int hashCode() {
    int hash = 7;
    hash = 71 * hash + this.x;
    hash = 71 * hash + this.y;
    return hash;
}



@Override
public boolean equals(Object other) 
{
    if (this == other)
       return true;

    if (!(other instanceof Point))
       return false;

    Point otherPoint = (Point) other;
    return otherPoint.x == x && otherPoint.y == y;
}