Java is a set of computer software and specifications that provides a software platform for developing application software and deploying it in a cross-platform computing environment. Java is used in a wide variety of computing platforms from embedded devices and mobile phones to enterprise servers and supercomputers. Java applets, which are less common than standalone Java applications, were commonly run in secure, sandboxed environments to provide many features of native applications through being embedded in HTML pages.
Writing in the Java programming language is the main way to produce code that will be deployed as byte code in a Java virtual machine (JVM); byte code compilers are also available for other languages, including Ada, JavaScript, Kotlin (Google's preferred Android language), Python, and Ruby. In addition, several languages have been designed to run natively on the JVM, including Clojure, Groovy, and Scala. Java syntax borrows heavily from C and C++, but object-oriented features are modeled after Smalltalk and Objective-C. Java eschews certain low-level constructs such as pointers and has a very simple memory model where objects are allocated on the heap (while some implementations e.g. all currently supported by Oracle, may use escape analysis optimization to allocate on the stack instead) and all variables of object types are references. Memory management is handled through integrated automatic garbage collection performed by the JVM.
Latest version The latest version is Java 26 released in March 2026.
The latest long-term support (LTS) version, Java 25 released in September 2025, it is one of a few LTS versions still supported, down to Java 8 LTS. Oracle extended support for Java 6 ended in December 2018.
As an open source platform, Java has many distributors, including Amazon, IBM, Azul Systems, and AdoptOpenJDK. Distributions include Amazon Corretto, Zulu, AdoptOpenJDK, and Liberica. Regarding Oracle, it distributes Java 8, and also makes available e.g. Java 11, both also currently supported LTS versions. Oracle (and others) "highly recommend that you uninstall older versions of Java" than Java 8, because of serious risks due to unresolved security issues.
Since Java 9 (as well as versions 10, 12–16, 18–20, and 22–24) are no longer supported, Oracle advises its users to "immediately transition" to a supported version.
Oracle released the last free-for-commercial-use public update for the legacy Java 8 LTS in January 2019, and will continue to support Java 8 with public updates for personal use indefinitely.
Platform The Java platform is a suite of programs that facilitate developing and running programs written in the Java programming language. A Java platform includes an execution engine (called a virtual machine), a compiler and a set of libraries; there may also be additional servers and alternative libraries that depend on the requirements. Java platforms have been implemented for a wide variety of hardware and operating systems with a view to enable Java programs to run identically on all of them.
The Java platform consists of several programs, each of which provides a portion of its overall capabilities. For example, the Java compiler, which converts Java source code into Java bytecode (an intermediate language for the JVM), is provided as part of the Java Development Kit (JDK). The Java Runtime Environment (JRE), complementing the JVM with a just-in-time (JIT) compiler, converts intermediate bytecode into native machine code on the fly. The Java platform also includes an extensive set of libraries.
The essential components in the platform are the Java language compiler, the libraries, and the runtime environment in which Java intermediate bytecode executes according to the rules laid out in the virtual machine specification.
Application domains Different platforms target different classes of device and application domains: Java Card: A technology that allows small Java-based applications (applets) to be run securely on smart cards and similar small-memory devices. Java ME (Micro Edition): Specifies several different sets of libraries (known as profiles) for devices with limited storage, display, and power capacities. It is often used to develop applications for mobile devices, PDAs, TV set-top boxes, and printers. Java SE (Standard Edition): For general-purpose use on desktop PCs, servers and similar devices. Jakarta EE (Enterprise Edition): Java SE plus various APIs which are useful for multi-tier client–server enterprise applications.
Java SE
Jakarta EE
Java virtual machine
The heart of the Java platform is the "virtual machine" that executes Java bytecode programs. This bytecode is the same no matter what hardware or operating system the program is running under. However, new versions, such as for Java 10 (and earlier), have made small changes, meaning the bytecode is in general only forward compatible. There is a just in time (JIT) compiler within the Java virtual machine (JVM). The JIT compiler translates the Java bytecode into native processor instructions at run-time and caches the native code in memory during execution.
The use of bytecode as an intermediate language permits Java programs to run on any platform that has a virtual machine available. The use of a JIT compiler means that Java applications, after a short delay during loading and once they have "warmed up" by being all or mostly JIT-compiled, tend to run about as fast as native programs. Since JRE version 1.2, Sun's JVM implementation has included a just-in-time compiler instead of an interpreter.
Although Java programs are cross-platform or platform independent, the code of the Java virtual machines (JVM) that execute these programs is not. Every supported operating platform has its own JVM.
Java Development Kit
Java Runtime Environment
The Java Runtime Environment (JRE) released by Oracle is a freely available software distribution containing a stand-alone JVM (HotSpot), the Java standard library (Java Class Library), a configuration tool, and—until its discontinuation in JDK 9—a browser plug-in. It is the most common Java environment installed on personal computers in the laptop and desktop form factor. Mobile phones including feature phones and early smartphones that ship with a JVM are most likely to include a JVM meant to run applications targeting Micro Edition of the Java platform. Meanwhile, most modern smartphones, tablet computers, and other handheld PCs that run Java apps are most likely to do so through support of the Android operating system, which includes an open source virtual machine incompatible with the JVM specification. (Instead, Google's Android development tools take Java programs as input and output Dalvik bytecode, which is the native input format for the virtual machine on Android devices.) The last Critical Path Update version of JRE with an Oracle BCL Agreement was 8u201 and, the last Patch Set Update version with the same license was 8u202. The last Oracle JRE implementation, regardless of its licensing scheme, was 9.0.4. Since Java Platform SE 9, the whole platform also was grouped into modules. The modularization of Java SE implementations allows developers to bundle their applications together with all the modules used by them, instead of solely relying on the presence of a suitable Java SE implementation in the user device.
Class libraries
In most modern operating systems (OSs), a large body of reusable code is provided to simplify the programmer's job. This code is typically provided as a set of dynamically loadable libraries that applications can call at runtime. Because the Java platform is not dependent on any specific operating system, applications cannot rely on any of the pre-existing OS libraries. Instead, the Java platform provides a comprehensive set of its own standard class libraries containing many of the same reusable functions commonly found in modern operating systems. Most of the system library is also written in Java. For instance, the Swing library paints the user interface and handles the events itself, eliminating many subtle differences between how different platforms handle components.
The Java class libraries serve three purposes within the Java platform. First, like other standard code libraries, the Java libraries provide the programmer a well-known set of functions to perform common tasks, such as maintaining lists of items or performing complex string parsing. Second, the class libraries provide an abstract interface to tasks that would normally depend heavily on the hardware and operating system. Tasks such as network access and file access are often heavily intertwined with the distinctive implementations of each platform. The java.net and java.io libraries implement an abstraction layer in native OS code, then provide a standard interface for the Java applications to perform those tasks. Finally, when some underlying platform does not support all of the features a Java application expects, the class libraries work to gracefully handle the absent components, either by emulation to provide a substitute, or at least by providing a consistent way to check for the presence of a specific feature.
Languages
The word "Java", alone, usually refers to Java programming language that was designed for use with the Java platform. Programming languages are typically outside of the scope of the phrase "platform", although the Java programming language was listed as a core part of the Java platform before Java 7. The language and runtime were therefore commonly considered a single unit. However, an effort was made with the Java 7 specification to more clearly treat the Java language and the Java virtual machine as separate entities, so that they are no longer considered a single unit.
Third parties have produced many compilers or interpreters that target the JVM. Some of these are for existing languages, while others are for extensions to the Java language. These include: BeanShell – a lightweight scripting language for Java (see also JShell) Ceylon – an object-oriented, strongly and statically typed programming language with an emphasis on immutability (and is no longer maintained since 2023) Clojure – a modern, dynamic, and functional dialect of the Lisp language on the Java platform Gosu – a general-purpose JVM-based programming language released under the Apache License 2.0 Groovy – a fully Java-interoperable, Java-syntax-compatible, static and dynamic language with features from Python, Ruby, Perl, and Smalltalk JRuby – a Ruby interpreter Jython – a Python interpreter Kotlin – a language for a JVM (and non-JVM, for e.g., desktop and iOS) with full Java interoperability (Google's preferred language for Android, its JVM, over Java, which is also still supported there and it previously promoted) Rhino – a JavaScript interpreter Scala – a multi-paradigm programming language with non-Java compatible syntax designed as a "better Java"
Similar platforms
The success of Java and its write once, run anywhere concept has led to other similar efforts, notably the .NET Framework, appearing since 2002, which incorporates many of the successful aspects of Java. .NET was built from the ground-up to support multiple programming languages, while the Java platform was initially built to support only the Java language, although many other languages have been made for JVM since. Like Java, .NET languages compile to byte code and are executed by the Common Language Runtime (CLR), which is similar in purpose to the JVM. Like the JVM, the CLR provides memory management through automatic garbage collection, and allows .NET byte code to run on multiple operating systems.
.NET included a Java-like language first named J++, then called Visual J# that was incompatible with the Java specification. It was discontinued 2007, and support for it ended in 2015.
Performance