Uniqe object in list

Question

Hi. I have a program something like below.
List<Edge> openEdge = new ArrayList<Edge>();
List<Edge>closedEdge = new ArrayList<Edge>();
openEdge.add(e);  // e is a edge object
while(openEdge.size() > 0){
     Edge process = openEdge.remove(0);
     if(!closedEdge.contains(process){
           closedEdge.add(process);
     if(//ceratin condition met){
           List<Edge> outList = graph.getNode(process.getStartid).getOutList();
          for(int i = 0; i < outList.size(); i++){
               Edge relax = outList.get(i);
               if(!openEdge.contains(relax)){
                      openEdge.add(relax);
}I want my entries in openEdge and closedEdge without duplicate entry, I mean openEdge and closedEdge can have same Edge entry, but within the same list, duplicate entry is not allowed. I know java API provides Set implementation such as HashSet and LinkedHashSet.
But the problem I am facing is, I want to remove the Edges from the list in the order of their insertion.
Using List is not a problem at all. However, when i have a huge number of entries for each list, the computational time degrades and program becomes very slow.
The openEdge list entries go around 20,000.
What i did to make the program faster was i created two hashset and used it to prevent the insertion of same entry. This makes the program fast, but requires extra memory to hold the HashSet.
Is there a better solution for this? The closedEdge always starts with 0, and openEdge with 1, and the entries is of around 20,000. The contains method is making the program very slow as it requires checking the whole list,in worst case, each time in the insertion procedure.
Any advice on how to go on with this.
Thank you.

Answer 1

Let's see if posting this message finally works (fcking slow forum today!)
If you try it like this, it should get considerable improve the speed:
class EdgeList {
    private Set<Edge> edgeSet;
    private List<Edge> edgeList;
    public EdgeList() {
        edgeSet = new HashSet<Edge>();
        edgeList = new ArrayList<Edge>();
    public void add(Edge e) {
        if(edgeSet.add(e)) { // true if edgeSet did not already contain 'e'
            edgeList.add(e); // will be in order of insertion
    public List<Edge> getEdges() {
        return edgeList;
class Edge {
    // don't forget tho override the equals(...) and hashCode() methods!
}