Pronounced jay sharp, a Microsoft-supported language for .NET. J# is Microsoft's implementation of the Java programming language. It is specifically designed to allow Java-language developers to easily transition to the .NET Framework and to create .NET applications.
J# applications are not compatible with the Java Virtual Machine (JVM) or the Java 2 platform. However, J# applications can be written using Visual Studio .NET and then compiled using third-party Java tools.
J# also is referred to as Visual J#.