scale4j
· scale4j is an open source project which built on top of well-known open source frameworks designed
to help you develop high-performance data-distributed systems with minimal effort
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 scale4j-aggregator-0.2.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.