JDK

The Java Development Kit (JDK) is a software development kit used to develop Java applications. It bundles the Java Runtime Environment (JRE) along with the toolset required for development, including a compiler, a debugger, and standard libraries. Core tools within the JDK include javac (the Java compiler), java (the runtime launcher), javadoc (documentation generator), jar (archiver), and jdb (debugger). In addition to these tools, the JDK provides the Java class libraries that constitute the Java API used by developers.

Java programs are written in source code and compiled by javac into bytecode, which is executed by the Java Virtual Machine (JVM). Because the bytecode runs on any platform with a compatible JVM, Java programs are cross-platform by design, enabling the same code to run on Windows, macOS, Linux, and other environments.

Historically developed by Sun Microsystems and now maintained by Oracle, Java is also produced as OpenJDK, an open-source reference implementation. Oracle JDK and OpenJDK are common distributions; many vendors provide OpenJDK builds. Licensing and support terms have varied across releases, with OpenJDK generally available under GPL with a classpath exception, while Oracle’s JDK has its own licensing model.

Java uses a release cadence with long-term support (LTS) versions at intervals, such as Java 8, 11, 17, and 21. Developers select a JDK version for development and deployment, and obtain platform-specific installers for Windows, macOS, and Linux. The JDK remains the standard toolkit for building, testing, and packaging Java applications.