Java is a general-purpose, object-oriented programming language developed by Sun Microsystems (later acquired by Oracle). Its first public release came in 1995. Today Java is one of the most widely used languages in the world — it powers enterprise systems, Android applications, web services, embedded devices, and cloud platforms.
General-purpose, object-oriented language
Developed by Sun Microsystems → acquired by Oracle
First release: 1995
One of the most widely used languages in the world
Powers: enterprise systems, Android, web services, embedded devices, cloud
The Key Idea: Write Once, Run Anywhere
The core principle of Java is portability. Source code is not compiled into machine code for a specific processor; instead it is compiled into bytecode — an intermediate representation. The bytecode is executed by the JVM, which is available on all major platforms.
Click to see where one .jar file runs ▶
HelloWorld.jar
🪟Windows
🐧Linux
🍎macOS
ℹ️WORA (Write Once, Run Anywhere) has been Java's motto since 1995. It still holds true: a .jar file built on Windows will run unchanged on a Linux server.
How Java Works: From Source to Execution
The execution of a Java program involves three stages. First you write source code in .java files. Then the javac compiler converts it to bytecode (.class files). Finally the JVM interprets or JIT-compiles the bytecode into native machine instructions.
Click to animate the compilation pipeline ▶
📝
.java
Source code
→
⚙️
javac
Compiler
→
📦
.class
Bytecode
→
🖥️
JVM
Virtual machine
→
✅
Output
Result
JDK, JRE and JVM — What's the Difference
Three terms are often confused, but they are nested: JVM is the core that executes bytecode; JRE adds the standard libraries; JDK adds the compiler and developer tools on top.
Hover over a ring to see what it contains
Hover over a ring to see what it contains
ℹ️For development always install the JDK — it includes everything you need. Starting with Java 11, Oracle no longer ships a standalone JRE.
Java Versions and LTS Releases
Since 2017 Java follows a predictable release cadence: a new version every 6 months. Certain versions are designated LTS (Long-Term Support) and receive security updates for several years.
Click a version to see its key features
2014
8
LTS
2018
11
LTS
2021
17
LTS
2023
21
LTS
2025
25
LTS
2026
26
Where Java is Used
Java is present in virtually every area of software development — from banking systems and Android apps to big data pipelines and cloud platforms.
Click a card to learn more
🏦
Enterprise
📱
Android
📊
Big Data
🎮
Games
☁️
Cloud
🌐
Web
Language Features
Java has several characteristics that set it apart. Strong static typing eliminates a whole class of bugs at compile time. The Garbage Collector frees developers from manual memory management. Built-in multithreading support and the vast Maven Central ecosystem complete the picture.
💀 = unreachable objects (freed by GC) | ✅ = live objects
idle
Stack
Thread.main() {
}
Heap
Young generation
Eden
S0
S1
Old generation (Tenured)
allocated
0
minor GC
0
major GC
0
freed
0
✅Java consistently ranks in the top three most in-demand programming languages across all major indexes (TIOBE, RedMonk, Stack Overflow). Knowledge of Java opens doors to enterprise, Android, cloud, and distributed-systems roles.