CODEWITHSUNDEEP
javahashmapdeep-copy
A. H.
A. H.

Reputation: 11

deep copy for a graph using hashmap does not work

I have a directed graph having edges as Map<E,Pair<V>>, and vertices as <V>.

I want to have a copy of this graph and make some changes in the copy while the original graph does not change.

I have written two different copying functions, copy1 and copy2. The second function works fine, however, in copy1, if I remove a vertix from the copy graph, it would be also removed from the original one. Can you tell me what the problem is with copy1 and how can I make a fast copy of my graph?

public Graph<V> copy1() {
        Graph<V> g = new Graph<V>();
        g.vertices.putAll(super.vertices);
        g.edges.putAll(super.edges);
        return g;
    }

public static  void copy2(IGraph<E> graph, IGraph<E> copy) {
        assert (copy.getVertexCount() == 0);

        for (E resource : graph.getVertices()) {
            copy.addVertex(resource);
        }
        for (Edge edge : graph.getEdges()) {
            Pair<E> endpoints = graph.getEndpoints(edge);
            copy.addEdge(edge, endpoints);
        }
    }

Upvotes: 1

Views: 236

Answers (1)

K Adithyan
K Adithyan

Reputation: 396

Use this as a method, so that it is perfect deepCopy with all objects newly created recursively

public static <T extends Serializable> T deepCopy(T o) throws Exception
{
    if (o == null)
        return null;

    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    ObjectOutputStream oos = new ObjectOutputStream(bos);

    oos.writeObject(o);
    bos.close();
    oos.close();

    ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
    ObjectInputStream ois = new ObjectInputStream(bis);

    T t = (T) ois.readObject();
    bis.close();
    ois.close();
    return t;
}

Upvotes: 1

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