The other replies kind of hit on this, but I'll expand on it by saying:

The collection creation methods existed because Java could perform type inference on methods but could not on constructors:

  // Java 1.5
  Map<String,Integer> map = new HashMap<String,Integer>();
  // Guava
  Map<String,Integer> map = Maps.newHashMap();
  // Java 1.8 diamond notation
  Map<String,Integer> map = new HashMap<>();