| JAIN | Java APIs for Integrated Networks |
| JAMA | Japanese Automobile Manufacturers Association |
| JCAT | Java Coordination and Transactions |
| JCC | Jain Call Control |
| JCP | Java Community Process |
| JDMK | Java Dynamic Management Kit |
| JEDEC | Joint Electron Device Engineering Council |
| JIT | Just in Time |
| JMAPI | Java Management Application Programming Interface |
| JMX | Java Management Extension |
| JPEG | Joint Photographic Experts Group |
| JSCE | JAIN Service-Creation Environment |
| JSIP | Java Session Initiation Protocol |
| JSLEE | JAIN Service Logic Execution Environment |
| JSP | Java Server Pages |
| J-TACS | Japan Total Access Communications System |
| JTAG | Joint Test Action Group |
| JTAPI | Java Telephony Application Programming Interface |
| JTRS | Joint Tactical Radio Systems |
| JVM | Java Virtual Machine |