android/guava/src/com/google/common/collect/Collections2.java
static boolean containsAllImpl(Collection<?> self, Collection<?> c) {
    for (Object o : c) {
      if (!self.contains(o)) {
        return false;
      }
    }
    return true;
  }
static boolean containsAllImpl(Collection<?> self, Collection<?> c) {
    for (Object o : c) {
      if (!self.contains(o)) {
        return false;
      }
    }
    return true;
  }
Returns {@code true} if the collection {@code self} contains all of the elements in the
collection {@code c}.

<p>This method iterates over the specified collection {@code c}, checking each element returned
by the iterator in turn to see if it is contained in the specified collection {@code self}. If
all elements are so contained, {@code true} is returned, otherwise {@code false}.

@param self a collection which might contain all elements in {@code c}
@param c a collection whose elements might be contained by {@code self}