Mac OS X - Wikipedia, the free encyclopedia: "tems. The OpenStep APIs are still available, but Apple now calls the technology Cocoa. (This heritage is visible in the Cocoa APIs, in which the class names mostly begin with 'NS' for NEXTSTEP.) A fourth option for developers is to write applications in the Java platform, which Mac OS X has supported as a 'first class citizen' — in practice this means that Java applications fit as neatly into the operating system as possible while still being 'cross-platform', and that GUIs, while being written in Swing, look almost exactly like native Cocoa interfaces."