Just discovered the Guava libraries project.
Do these work with GWT?
Here are some more details on how to accomplish this with the (currently latest) 19.0 release of Guava.
The Guava release consists of two JARs, guava-19.0.jar and guava-gwt-19.0.jar. You will need both for getting Guava to work within your GWT project. (In a non-GWT project you will only need the former.) Download them and add them to your project; if you use Maven, use these dependencies:
com.google.guava
guava
19.0
com.google.guava
guava-gwt
19.0
Maven will then automatically download the two Jars from the Central Maven Repository, see also the Guava page on mvnrepositories. As an SBT user, you would go for something like libraryDependencies += "com.google.guava" % "guava" % "19.0".
Add
to your GWT module file to enable Guava.