Stuff

    public VertexIterator adjacentVertices(int v) throws IllegalArgumentException {        if (v < 0 || v >= numVertices) {            throw new IllegalArgumentException(                "Out of range: v = " + v);        }        return new AdjacentVerticesIterator(v);    }        private class AdjacentVerticesIterator(int v) implements VertexIterator {        private Iterator<Integer> setIterator;                AdjacentVerticesIterator(int v) {            setIterator = adjacentVertices[v];    }