Java is an object-oriented programming language developed by Sun Microsystems.
Java Database Connectivity (JDBC) is a standard Structured Query Language (SQL) data access interface developed by Sun Microsystems that allows Java applications to access databases.
Jet is a Microsoft database engine technology developed in 1992 and included in a variety of Microsoft products, including Microsoft Access and Microsoft Visual Basic.
Jacket, in networking, is the outer covering of cabling that protects it from physical damage.
JACK is a receptacle into which you can insert a connector or plug to form a connection.