android/guava/src/com/google/common/graph/EndpointPair.java
public static <N> EndpointPair<N> ordered(N source, N target) {
    return new Ordered<N>(source, target);
  }
public static <N> EndpointPair<N> ordered(N source, N target) {
    return new Ordered<N>(source, target);
  }
Returns an {@link EndpointPair} representing the endpoints of a directed edge.