Vertex[] getSinks() {
		int i = 0, n, j = 0;

		n = numSinks();
		Vertex[] answer = new Vertex[n];

		while ((j < n) && (i < nextIndex)) {
			if ((firstOutgoingEdge[i] == null) && (vertices[i] != null)) {
				answer[j++] = vertices[i];
			}
			i++;
		}
		return answer;
	}
Return a Vertex[] containing all vertices in the VertexSet that
have no outgoing edges. If there are none an array of length 0 
will be returned.
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/VertexSet.java