Download org.eclipse.pde.org.eclipse.pde.api.tools.ee.osgiminimum12.1.0.300.org.eclipse.pde : org.eclipse.pde.tools.versioning JAR file - All Versions:
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 org.eclipse.pde.tools.versioning-1.0.200.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.