gwtx
· The goal of GWTx is to provide drop in support for an extended
set of the of the standard Java library classes on top of what
is provided by the GWT distribution provided by Google
Download JD-GUI to open JAR file and explore Java source code file (.class .java)
Click menu "File → Open File..." or just drag-and-drop the JAR file in the JD-GUI window gwtx-1.5.3.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.