Graph interface

public interface IGraph {
    public int vertCount();

    int first(int vert);
    int next(int vert, int last);
    void addEdge(int vertex, int neighbor, float weight);
    void removeEdge(int vertex, int neighbor);
    boolean isEdge(int vertex, int neighbor);
    Float getEdge(int vertex, int neighbor);
    default List<Integer> getNeighbors(int vertex) {
        List<Integer> ret = new ArrayList<>(vertCount());
        for(int i=first(vertex);i<vertCount();i = next(vertex,i)) {
            ret.add(i);
        }
        return ret;
    }
    //num neighbors
    int degree(int vertex);
}