/**
   * Adds the given edge to those to be displayed in the viewer. Note that the edge must connect
   * nodes that have already been added to the viewer. This version will use the locations of the
   * two nodes to calculate their distance of separation.
   *
   * @param edge Edge to add to the display.
   * @return True if edge was added successfully. False if edge contains nodes that have not been
   *     added to the viewer.
   */
  public boolean addEdge(E edge) {
    Particle p1 = nodes.get(edge.getNode1());
    if (p1 == null) {
      System.err.println("Warning: Node1 not found when creating edge.");
      return false;
    }
    Particle p2 = nodes.get(edge.getNode2());
    if (p2 == null) {
      System.err.println("Warning: Node2 not found when creating edge.");
      return false;
    }

    // Only add edge if it does not already exist in the collection
    if (!edges.containsKey(edge)) {
      float x1 = p1.position().x();
      float y1 = p1.position().y();
      float x2 = p2.position().x();
      float y2 = p2.position().y();
      // Strength, damping, reset length
      edges.put(
          edge,
          physics.makeSpring(
              p1,
              p2,
              EDGE_STRENGTH,
              DAMPING,
              (float) Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2))));
    }
    return true;
  }
  /**
   * Adds the given edge to those to be displayed in the viewer. Note that the edge must connect
   * nodes that have already been added to the viewer. This version will fix the distance of
   * separation between nodes to the given value
   *
   * @param edge Edge to add to the display.
   * @return True if edge was added successfully. False if edge contains nodes that have not been
   *     added to the viewer.
   */
  public boolean addEdge(E edge, float distance) {
    Particle p1 = nodes.get(edge.getNode1());
    if (p1 == null) {
      System.err.println("Warning: Node1 not found when creating edge.");
      return false;
    }
    Particle p2 = nodes.get(edge.getNode2());
    if (p2 == null) {
      System.err.println("Warning: Node2 not found when creating edge.");
      return false;
    }

    // Only add edge if it does not already exist in the collection
    if (!edges.containsKey(edge)) {
      // Strength, damping, reset length
      edges.put(edge, physics.makeSpring(p1, p2, EDGE_STRENGTH, DAMPING, distance));
    }
    return true;
  }