javac - Java Compiler

Complete reference for the Java programming language compiler including all command-line options and usage examples

The javac tool reads Java source files and compiles them into Java class files. The compiler is implemented in the jdk.compiler module.

Basic Usage

javac [options] [source files]

Source Code

The javac implementation is located at:

• Main class: src/jdk.compiler/share/classes/com/sun/tools/javac/Main.java:1
• Options: src/jdk.compiler/share/classes/com/sun/tools/javac/main/Option.java:1
• Core compiler: src/jdk.compiler/share/classes/com/sun/tools/javac/main/JavaCompiler.java:1

Standard Options

Classpath and Module Path

--class-path · path

Specify where to find user class files and annotation processors. Can also use -classpath or -cp.

javac -cp lib/commons.jar:lib/utils.jar MyClass.java

--module-path · path

Specify where to find application modules. Can also use -p.

javac --module-path mods -d build/modules src/module-info.java src/com/example/*.java

--source-path · path

Specify where to find input source files. Can also use -sourcepath.

javac -sourcepath src -d build src/com/example/Main.java

--module-source-path · module-pattern

Specify where to find input source files for multiple modules.

javac --module-source-path "src/*" -d build $(find src -name '*.java')

Output Control

-d · directory

Specify where to place generated class files.

javac -d build/classes src/**/*.java

-s · directory

Specify where to place generated source files (from annotation processors).

javac -s generated -d build MyAnnotatedClass.java

-h · directory

Specify where to place generated native header files.

javac -h native/include -d build NativeClass.java

Source and Target Versions

--source · release

Provide source compatibility with the specified Java SE release. Can also use -source.

Supported values include: 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23

javac --source 17 --target 17 OldCode.java

--target · release

Generate class files suitable for the specified Java SE release. Can also use -target.

javac --target 11 -d build src/*.java

--release · release

Compile for a specific Java SE release. Sets source, target, and bootstrap classpath.

javac --release 17 src/com/example/*.java

Module System Options

--module · module-name

Compile only the specified module. Can also use -m.

javac --module com.example.myapp --module-path mods

--add-modules · module-list

Root modules to resolve in addition to the initial modules.

javac --add-modules java.sql,java.xml -d build src/*.java

--limit-modules · module-list

Limit the universe of observable modules.

javac --limit-modules java.base,java.logging -d build src/*.java

--add-exports · module/package=target-module

Export a package from a module to other modules.

javac --add-exports java.base/sun.nio.ch=ALL-UNNAMED MyClass.java

--add-reads · module=target-module

Update a module to read another module.

javac --add-reads com.example.app=com.example.utils src/*.java

Annotation Processing

-proc · none|only|full

Control annotation processing and compilation.

• none: No annotation processing
• only: Only annotation processing, no compilation
• full: Both annotation processing and compilation (default)

javac -proc:none src/*.java

-processor · class-list

Names of annotation processors to run.

javac -processor com.example.MyProcessor,com.example.OtherProcessor src/*.java

--processor-path · path

Specify where to find annotation processors. Can also use -processorpath.

javac -processorpath processors.jar -processor MyProcessor src/*.java

Debugging and Diagnostics

-g · none

Generate all debugging information (default).

javac -g src/*.java

-g:none · none

Generate no debugging information.

javac -g:none src/*.java

-g: · lines,vars,source

Generate only specified kinds of debugging information.

javac -g:lines,source src/*.java

-verbose · none

Output messages about what the compiler is doing.

javac -verbose src/com/example/Main.java

Warnings and Errors

-Xlint · none

Enable all recommended warnings.

javac -Xlint src/*.java

-Xlint: · key-list

Enable or disable specific warnings. Use -Xlint:key to enable or -Xlint:-key to disable.

Available keys: cast, classfile, deprecation, dep-ann, divzero, empty, exports, fallthrough, finally, missing-explicit-ctor, module, opens, options, overloads, overrides, path, processing, rawtypes, removal, requires-automatic, requires-transitive-automatic, serial, static, try, unchecked, varargs, preview

javac -Xlint:unchecked,deprecation src/*.java
javac -Xlint:-serial src/*.java

-Werror · none

Terminate compilation if warnings occur.

javac -Werror -Xlint:all src/*.java

-nowarn · none

Generate no warnings.

javac -nowarn src/*.java

Preview Features

--enable-preview · none

Enable preview language features.

javac --enable-preview --source 23 PreviewFeature.java

Extended Options

Maximum Errors/Warnings

-Xmaxerrs · number

Set the maximum number of errors to print.

javac -Xmaxerrs 5 src/*.java

-Xmaxwarns · number

Set the maximum number of warnings to print.

javac -Xmaxwarns 10 src/*.java

DocLint

-Xdoclint · none

Enable recommended checks for problems in javadoc comments.

javac -Xdoclint src/*.java

-Xdoclint: · group-list

Enable or disable specific checks. Groups: accessibility, html, missing, reference, syntax

javac -Xdoclint:all,-missing src/*.java

Other Extended

-Xplugin: · plugin-name

Name and optional arguments for a javac plugin.

javac -Xplugin:MyPlugin arg1 arg2 src/*.java

-Xprefer: · source|newer

Specify which file to read when both source and class files are found.

javac -Xprefer:source -cp build src/*.java

Common Usage Examples

Compile Simple Application

# Compile single file
javac HelloWorld.java

# Compile multiple files
javac *.java

# Compile with output directory
javac -d build src/**/*.java

Compile Modular Application

# Compile module with module-info.java
javac -d mods/com.example.app \
      --module-source-path src \
      $(find src/com.example.app -name '*.java')

# Compile multiple modules
javac -d mods \
      --module-source-path src \
      --module com.example.app,com.example.utils

Compile with Dependencies

# With classpath
javac -cp lib/gson.jar:lib/commons-lang3.jar \
      -d build \
      src/com/example/*.java

# With module path
javac --module-path mods:libs \
      --add-modules com.google.gson \
      -d build \
      src/module-info.java src/com/example/*.java

Cross-Version Compilation

# Compile for Java 11 compatibility
javac --release 11 -d build src/*.java

# Compile with specific source and target
javac --source 17 --target 17 -d build src/*.java

Annotation Processing

# Run annotation processors
javac -processor lombok.launch.AnnotationProcessorHider$AnnotationProcessor \
      -cp lombok.jar \
      -d build \
      src/*.java

# Generate source to specific directory
javac -s generated \
      -processor com.example.CodeGenerator \
      -d build \
      src/*.java

Information Options

--help · none

Print a synopsis of standard options. Can also use -help, -h, or -?.

javac --help

--help-extra · none

Print help on extra options. Can also use -X.

javac -X

--version · none

Print version information. Can also use -version.

javac --version

The javac compiler supports reading options from files using @filename. This is useful for long command lines:

javac @options.txt @sources.txt

where options.txt contains:

-d build
-cp lib/dep1.jar:lib/dep2.jar
-Xlint:all

When compiling for older Java versions using --release, javac automatically uses the correct API signatures to prevent using APIs not available in the target version.

Exit Codes

• 0: Successful compilation
• 1: Compilation errors occurred
• 2: Invalid command-line arguments
• 3: System error or resource exhaustion
• 4: Abnormal termination

See Also

• java - Java application launcher
• javadoc - API documentation generator
• jar - JAR file tool