Crashczyk library
· Android library that allows launching a custom activity when your app crashes, instead of showing the hated "Unfortunately, X has stopped" dialog.
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 crashczyk-1.0.0.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.