Method roots

output/java_guava/1.4.17/GraphProperties.java:102–110

Returns the set of all nodes in graph that have no predecessors. Note that in an undirected graph, this is equivalent to all isolated nodes.

(Graph<N> graph)

  public static <N> ImmutableSet<N> roots(Graph<N> graph) {
    ImmutableSet.Builder<N> builder = ImmutableSet.builder();
    for (N node : graph.nodes()) {
      if (graph.predecessors(node).isEmpty()) {
        builder.add(node);
      }
    }
    return builder.build();
  }
}