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 android-helpshift-withCampaigns-aar-java7-7.6.3-withCampaigns-java7.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.