javac - Java Compiler

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

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
DocLint
Other Extended

-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

-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

-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

Get Started

Building the JDK

Architecture

Development

Tools & Utilities

javac - Java Compiler

Basic Usage

Source Code

Standard Options

Classpath and Module Path

Output Control

Source and Target Versions

Module System Options

Annotation Processing

Debugging and Diagnostics

Warnings and Errors

Preview Features

Extended Options

Common Usage Examples

Compile Simple Application

Compile Modular Application

Compile with Dependencies

Cross-Version Compilation

Annotation Processing

Information Options

Exit Codes

See Also

Build docs developers (and LLMs) love

Get Started

Building the JDK

Architecture

Development

Tools & Utilities

​Basic Usage

​Source Code

​Standard Options

​Classpath and Module Path

​Output Control

​Source and Target Versions

​Module System Options

​Annotation Processing

​Debugging and Diagnostics

​Warnings and Errors

​Preview Features

​Extended Options

​Common Usage Examples

​Compile Simple Application

​Compile Modular Application

​Compile with Dependencies

​Cross-Version Compilation

​Annotation Processing

​Information Options

​Exit Codes

​See Also

Build docs developers (and LLMs) love

Basic Usage

Source Code

Standard Options

Classpath and Module Path

Output Control

Source and Target Versions

Module System Options

Annotation Processing

Debugging and Diagnostics

Warnings and Errors

Preview Features

Extended Options

Common Usage Examples

Compile Simple Application

Compile Modular Application

Compile with Dependencies

Cross-Version Compilation

Annotation Processing

Information Options

Exit Codes

See Also