Oracle Corporation is the current owner of the official implementation of the Java SE platform. This implementation is based on the original implementation of Java by Sun. The Oracle implementation is available for Mac OS X, Windows and Solaris. Because Java lacks any formal standardization recognized by Ecma International, ISO/IEC, ANSI, or any other third-party standards organization, the Oracle implementation is the de facto standard.
The Oracle implementation are packaged into two different distributions. The Java Runtime Environment (JRE) which contains the parts of the Java SE platform required to run Java programs. This package is intended for end-users. The Java Development Kit (JDK), is intended for software developers and includes development tools such as the Java compiler, Javadoc, Jar, and a debugger.
OpenJDK is another notable Java SE implementation that is licensed under the GPL. The implementation started when Sun began releasing the Java source code under the GPL. As of Java SE 7, OpenJDK is the official Java reference implementation.
The goal of Java is to make all implementations of Java compatible. Historically, Sun’s trademark license for usage of the Java brand insists that all implementations be “compatible”. This resulted in a legal dispute with Microsoft after Sun claimed that the Microsoft implementation did not support RMI or JNI and had added platform-specific features of their own. Sun sued in 1997, and in 2001 won a settlement of US$20 million, as well as a court order enforcing the terms of the license from Sun. As a result, Microsoft no longer ships Windows with Java.
Platform-independent Java is essential to Java EE, and an even more rigorous validation is required to certify an implementation. This environment enables portable server-side applications.