It is common to encounter scenarios where someone attempts to delete a JAR file that is in use. This was a source of many reliability issues in the past, at least on Unix, when the CEN was mapped into memory. One remaining issue is specific to Windows and is because the Zip/JAR file is opened where we should consider opening JAR files with the FILE_SHARE_DELETE sharing mode. The implementation of the java.nio.file API uses this sharing mode by default, java.io does not. Note that the issue here is specific to Zip/JAR files opened by the java.util.zip/java.util.jar APIs, it is not a suggestion to change java.io as that has wider implications.