J2

J2 commonly refers to the Java 2 Platform, a major rebranding of Sun Microsystems' Java platform announced in 1998. It encompassed three editions designed for different deployment targets: J2SE (Standard Edition) for desktop and server applications, J2EE (Enterprise Edition) for enterprise-scale systems, and J2ME (Micro Edition) for mobile and embedded devices. The designation signaled a broad refresh of the language, runtime, and libraries to support a wider range of applications and environments.

J2SE provided the core runtime and libraries used by standard Java applications, including updates to the language, a revised set of standard APIs, and improved development tooling. J2EE extended Java capabilities for enterprise needs, offering APIs and specifications such as servlets, JavaServer Pages, Enterprise JavaBeans, and messaging for scalable, distributed applications. J2ME targeted devices with constrained resources, delivering a compact, configurable API surface for mobile, embedded, and other limited environments.

In 2006, Sun renamed the platform to Java Platform, Standard Edition (Java SE), Java Platform, Enterprise Edition (Java EE), and Java Platform, Micro Edition (Java ME). The J2 prefix gradually disappeared from official branding, aligning with Java’s version-based naming. Since then, Java SE, Java EE (renamed to Jakarta EE in the Eclipse Foundation collaboration), and Java ME have continued to evolve independently of the J2 branding. The term J2 remains historical, encountered primarily in older documentation and discussions about the evolution of Java.