extcheck - A utility to detect jar conflicts

extcheck detects version conflicts between a target jar file and currently installed extension jar files.


extcheck [ -verbose ] targetfile.jar


The extcheck utility checks a specified Jar file for title and version conflicts with any extensions installed in the JDKTM software. Before installing an extension, you can use this utility to see if the same or a more recent version of the extension is already installed.

The extcheck utility compares the Specification-title and Specification-version headers in the manifest of targetfile.jar file against the corresponding headers in all Jar files currently installed in the extension directory. (The extension directory is jre\lib\ext by default.) The extcheck utility compares version numbers in the same way as the method java.lang.Package.isCompatibleWith.

If no conflict is detected, the return code is 0.

If the manifest of any of the jar file in the extensions directory has the same Specification-title and the same or a newer Specification-version number, a non-zero error code is returned. A non-zero error code is also returned if targetfile.jar does not have the Specification-title or Specification-version attributes in its manifest.


Lists Jar files in the extension directory as they are checked. Additionally, manifest attributes of the target jar file and any conflicting jar files are also reported.