public String toString() {
    String s;
    s = "Vertices:\n";
    for (int i=0; i < current; i++) {
      s += "  " + i + ": " + locations[i].getName() + "\n";
    }
    s+="\n";
    s += "Edges:\n";
    for (int i=0; i < current; i++) {
      for (int j=0; j < i; j++) {
        if (adjacent[i][j]) {
          s+="  "+i+"->"+j+": "+weight[i][j]+"\n";
        }
      }
    }
    return s;
  }