What purpose do the collection classes defined under com.google.gwt.dev.util.collect.* serve?

Question

I accidentally used HashSet and HashMap defined under the package com.google.gwt.dev.util.collect in the client side code. Found out the package does not have a module xml file and hence these collection classes are not meant to be used on the client side.

What is the purpose of having these classes in the GWT SDK, if these aren't supposed to be used within the client package? There definitely has to be some benefit from these classes to merit inclusion in the SDK.

What am I missing?

Answer 1

Those collection implementations were written by Google engineers to improve the performance (specifically memory usage) of the GWT internals, such as the Java-to-JavaScript compiler. They are implementation details not intended to be part of the public API and should not be used by GWT developers.