What is a .java file?
Java Source File · Code and data · Sun Microsystems / Oracle · 1995
A .java file is Java source code, a widely used language that compiles to bytecode and runs on the Java Virtual Machine. It powers Android apps, enterprise back ends and large-scale systems.
What is a .java file used for?
Java source is compiled by javac into .class files of bytecode, which the JVM runs on any platform. This write-once, run-anywhere design made Java a mainstay of enterprise software.
Android apps were traditionally written in Java, and much server software still is. The files are plain text; IntelliJ IDEA, Eclipse and VS Code are common editors.
How to open a .java file
The .java format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .java file.
Windows
- IntelliJ IDEA
- Eclipse
- VS Code
macOS
- IntelliJ IDEA
- Eclipse
- VS Code
Linux
- IntelliJ IDEA
- Eclipse
- VS Code
How to convert a .java file
You can convert a .java file to class (bytecode), jar using a conversion tool or the export menu of an app that opens it.
.java file signature (magic bytes)
Programs recognise a .java file by the bytes at the start of the file, not by its name. These are the signatures for Java.
| Hex signature | Offset | Note |
|---|---|---|
| (no fixed signature) | 0 | plain text; no fixed magic bytes |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .java file?
A .java file is Java source code, a widely used language that compiles to bytecode and runs on the Java Virtual Machine. It powers Android apps, enterprise back ends and large-scale systems.
How do I compile and run a .java file?
Compile with javac File.java to make File.class, then run java File. Modern JDKs can also run a single file directly with java File.java.
What is the difference between .java and .class?
A .java file is human-readable source. javac compiles it into a .class file of bytecode that the Java Virtual Machine executes.
How do I open a .java file?
Any text editor works. IntelliJ IDEA, Eclipse or VS Code add highlighting, building and debugging.
Related formats
Sources
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