Electro Designs

.J62  Ricoh Camera File
  .JAR  Java Archive File  
  .JAS  Compressed Graphic
  .JAV  Java Source Code
  .JAVA  JBuilder Java File
  .JBC  Jam Byte-Code Hex File (8051 Microprocessor File)
        BestCrypt File
  .JBD  SigmaScan Data File
  .JBF  Paint Shop Pro Browser File
  .JBK  Juno Backup File
  .JBX  Project Scheduler File
  .JC!  FlashGet File
  .JDB  Siren Jukebox
  .JDE  Cariverona
  .JDF  Turok 2 Game File
  .JEF  Janome NH10000 Sewing Machine File
  .JET  Hybrid JetFax Fax
  .JFF  JPEG Image
  .JFI  Image File
  .JFX  J2 Fax File
  .JIF  JPEG Image
  .JIS  Japanese
  .JLF  JetLinks Bookmark Managment
  .JMP  SAS JMPDiscovery Chart-to-statistics File
  .JMS  Voxtron TeleButler Graphical Voice Response Call Flow
  .JN1  Epic MegaGames Jill of the Jungle Data File
  .JNB  Sigma Plot Workbook File
  .JNG  JPEG Network Graphic
  .JNK  Junk (temporary file)
  .JNL  Ingres Journal File
  .JOB  Job File
        Task Scheduler Task Object
        AI Research File
        QuestVision Vector Graphics File (IMG File Conversion)
  .JOR  MS SQL Server Journal File
  .JOU  VAX Edt Editor Journal Backup
  .JPC  Picture File (Japanese)
  .JPE  JPEG Image
  .JPG  JPEG Image  [Viewer]
  .JPL  Siren Jukebox
  .JS   JavaScript Source Code
  .JSB  Henter-Joyce, Inc. Jaws Script Binary File (Screen reader program)
  .JSD  eFAX Jet Suite Document
        Henter-Joyce, Inc. Jaws Script Documentation File (Screen reader program)
  .JSE  JScript Encoded Script File
  .JSH  Henter-Joyce, Inc. Jaws Script Header File (Screen reader program)
  .JSL  PaintShop Pro File
  .JSM  Henter-Joyce, Inc. Jaws Script Message File (Screen reader program)
  .JSP  Java Server Page
  .JSS  Henter-Joyce, Inc. Jaws Script Source File (Screen reader program)
  .JT   JT Fax  
  .JTD  Ichitaro 11 (major Japanese word proccesser)
  .JTF  JPEG Tagged Interchange Format Image
        Hayes JT Fax
  .JTK  Sun Java ToolKit File
  .JTP  JetForm File
  .JW   Justwrite Text
  .JWL  Justwrite Text File Library
  .JZZ  Jazz Spreadsheet