javac

Compile a .java file

$ javac [path/to/file.java]

$ javac [path/to/file1.java path/to/file2.java ...]

$ javac [*.java]

$ javac -d [path/to/directory] [path/to/file.java]

javac [options] sourcefile.java...

-classpath path, -cp path
    Specifies where to find user class files, overriding CLASSPATH environment variable

-d directory
    Specifies destination directory for compiled class files

-source version
    Sets source code language version (e.g., 8, 11, 17)

-target version
    Generates class files for specified VM version

-verbose
    Enables verbose output, showing compilation progress

-deprecation
    Shows locations of deprecated API uses

-g
    Generates all debugging information

-g:none
    Does not generate debugging information

-Xlint
    Enables all recommended warnings

-Xlint:suboption
    Enables specific category of warnings (e.g., unchecked, cast)

-Jflag
    Passes flag directly to the runtime system

-sourcepath path
    Specifies path to source files

-bootclasspath path
    Overrides location of bootstrap class files

-extdirs dirs
    Overrides extension directories

javac is the primary command-line compiler for the Java programming language, included in the Java Development Kit (JDK). It reads one or more .java source files containing Java class definitions and compiles them into platform-independent bytecode stored in .class files. These bytecode files are executed by the Java Virtual Machine (JVM) via the java command.

The compiler performs syntax analysis, type checking, flow analysis, and desugaring of syntactic constructs. It supports annotation processing, modular compilation (since Java 9), and generates metadata for debugging and optimization. Javac handles dependencies automatically via classpath scanning but requires explicit specification for external libraries.

Key features include support for generics, lambdas, modules, and records (Java 14+). Output can be directed to custom directories, with options for source/target compatibility, verbose logging, and warnings for deprecated APIs or unchecked operations. It's essential for building Java applications, libraries, and applets from source.

Requires JDK installation (not just JRE); handles multiple files but needs all dependencies on classpath; fails on syntax/type errors without generating partial output by default; modular apps (Java 9+) require --module-path or --module-source-path.

javac -d bin -cp lib/* src/*.java
Compiles all .java files in src/ to bin/, using libraries in lib/.

Use javac -X for extended options list; -Werror treats warnings as errors.

Introduced in JDK 1.0 (1996) by Sun Microsystems as the reference Java compiler. Evolved with language features like generics (JDK 5), modules (JDK 9), and preview features (JDK 12+). Maintained by Oracle in proprietary JDK and by OpenJDK community since 2006.

java(1), javap(1), jar(1), javadoc(1), jdb(1)