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."

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." questions.

."

.TH javac 1 "10 May 2011"

.LP

.SH "Name"

javac \- Java programming language compiler

.LP

.SH "SYNOPSIS"

.LP

.nf

\f3

.fl

        \fP\f3javac\fP [ options ] [ sourcefiles ] [ classes ] [ @argfiles ]

.fl

.fl

.fi

.LP

.LP

Arguments may be in any order.

.LP

.RS 3

.TP 3

options

Command\-line options.

.TP 3

sourcefiles

One or more source files to be compiled (such as MyClass.java).

.TP 3

classes

One or more classes to be processed for annotations (such as MyPackage.MyClass).

.TP 3

@argfiles

One or more files that lists options and source files. The \f2\-J\fP options are not allowed in these files.

.RE

.LP

.SH "DESCRIPTION"

.LP

.LP

The \f3javac\fP tool reads class and interface definitions, written in the Java programming language, and compiles them into bytecode class files. It can also process annotations in Java source files and classes.

.LP

.LP

There are two ways to pass source code file names to \f3javac\fP:

.LP

.RS 3

.TP 2

o

For a small number of source files, simply list the file names on the command line.

.TP 2

o

For a large number of source files, list the file names in a file, separated by blanks or line breaks. Then use the list file name on the \f3javac\fP command line, preceded by an \f3@\fP character.

.RE

.LP

.LP

Source code file names must have \f2.java\fP suffixes, class file names must have \f2.class\fP suffixes, and both source and class files must have root names that identify the class. For example, a class called \f2MyClass\fP would be written in a source file called \f2MyClass.java\fP and compiled into a bytecode class file called \f2MyClass.class\fP.

.LP

.LP

Inner class definitions produce additional class files. These class files have names combining the inner and outer class names, such as \f2MyClass$MyInnerClass.class\fP.

.LP

.LP

You should arrange source files in a directory tree that reflects their package tree. For example, if you keep all your source files in \f3/workspace\fP, the source code for \f2com.mysoft.mypack.MyClass\fP should be in \f3/workspace/com/mysoft/mypack/MyClass.java\fP.

.LP

.LP

By default, the compiler puts each class file in the same directory as its source file. You can specify a separate destination directory with \f3\-d\fP (see Options, below).

.LP

.SH "OPTIONS"

.LP

.LP

The compiler has a set of standard options that are supported on the current development environment and will be supported in future releases. An additional set of non\-standard options are specific to the current virtual machine and compiler implementations and are subject to change in the future. Non\-standard options begin with \f3\-X\fP.

.LP

.SS

Standard Options

.LP

.RS 3

.TP 3

\-Akey[=value]

Options to pass to annotation processors. These are not interpreted by javac directly, but are made available for use by individual processors. \f2key\fP should be one or more identifiers separated by ".".

.TP 3

\-cp path or \-classpath path

Specify where to find user class files, and (optionally) annotation processors and source files. This class path overrides the user class path in the \f3CLASSPATH\fP environment variable. If neither \f3CLASSPATH\fP, \f3\-cp\fP nor \f3\-classpath\fP is specified, the user class path consists of the current directory. See Setting the Class Path for more details.

.br

.br

>If the \f3\-sourcepath\fP option is not specified, the user class path is also searched for source files.

.br

.br

If the \f3\-processorpath\fP option is not specified, the class path is also searched for annotation processors.

.TP 3

\-Djava.ext.dirs=directories

Override the location of installed extensions.

.TP 3

\-Djava.endorsed.dirs=directories

Override the location of endorsed standards path.

.TP 3

\-d directory

Set the destination directory for class files. The directory must already exist; \f3javac\fP will not create it. If a class is part of a package, \f3javac\fP puts the class file in a subdirectory reflecting the package name, creating directories as needed. For example, if you specify \f3\-d /home/myclasses\fP and the class is called \f2com.mypackage.MyClass\fP, then the class file is called \f2/home/myclasses/com/mypackage/MyClass.class\fP.

.br

.br

If \f3\-d\fP is not specified, \f3javac\fP puts each class files in the same directory as the source file from which it was generated.

.br

.br

\f3Note:\fP The directory specified by \f3\-d\fP is not automatically added to your user class path.

.TP 3

\-deprecation

Show a description of each use or override of a deprecated member or class. Without \f3\-deprecation\fP, \f3javac\fP shows a summary of the source files that use or override deprecated members or classes. \f3\-deprecation\fP is shorthand for \f3\-Xlint:deprecation\fP.

.TP 3

\-encoding encoding

Set the source file encoding name, such as \f2EUC\-JP and UTF\-8\fP. If \f3\-encoding\fP is not specified, the platform default converter is used.

.TP 3

\-endorseddirs directories

Override the location of endorsed standards path.

.TP 3

\-extdirs directories

Overrides the location of the \f2ext\fP directory. The \f2directories\fP variable is a colon\-separated list of directories. Each JAR archive in the specified directories is searched for class files. All JAR archives found are automatically part of the class path.

.br

.br

If you are cross\-compiling (compiling classes against bootstrap and extension classes of a different Java platform implementation), this option specifies the directories that contain the extension classes. See Cross\-Compilation Options for more information.

.TP 3

\-g

Generate all debugging information, including local variables. By default, only line number and source file information is generated.

.TP 3

\-g:none

Do not generate any debugging information.

.TP 3

\-g:{keyword list}

Generate only some kinds of debugging information, specified by a comma separated list of keywords. Valid keywords are:

.RS 3

.TP 3

source

Source file debugging information

.TP 3

lines

Line number debugging information

.TP 3

vars

Local variable debugging information

.RE

.TP 3

\-help

Print a synopsis of standard options.

.TP 3

\-implicit:{class,none}

Controls the generation of class files for implicitly loaded source files. To automatically generate class files, use \f3\-implicit:class\fP. To suppress class file generation, use \f3\-implicit:none\fP. If this option is not specified, the default is to automatically generate class files. In this case, the compiler will issue a warning if any such class files are generated when also doing annotation processing. The warning will not be issued if this option is set explicitly. See Searching For Types.

.TP 3

\-Joption

Pass \f2option\fP to the \f3java\fP launcher called by \f3javac\fP. For example, \f3\-J\-Xms48m\fP sets the startup memory to 48 megabytes. It is a common convention for \f3\-J\fP to pass options to the underlying VM executing applications written in Java.

.br

.br

\f3Note:\fP \f3CLASSPATH\fP, \f3\-classpath\fP, \f3\-bootclasspath\fP, and \f3\-extdirs\fP do \f2not\fP specify the classes used to run \f3javac\fP. Fiddling with the implementation of the compiler in this way is usually pointless and always risky. If you do need to do this, use the \f3\-J\fP option to pass through options to the underlying \f3java\fP launcher.

.TP 3

\-nowarn

Disable warning messages. This has the same meaning as \f3\-Xlint:none\fP.

.TP 3

\-proc: {none,only}

Controls whether annotation processing and/or compilation is done. \f3\-proc:none\fP means that compilation takes place without annotation processing. \f3\-proc:only\fP means that only annotation processing is done, without any subsequent compilation.

.TP 3

\-processor class1[,class2,class3...]

Names of the annotation processors to run. This bypasses the default discovery process.

.TP 3

\-processorpath path

Specify where to find annotation processors; if this option is not used, the class path will be searched for processors.

.TP 3

\-s dir

Specify the directory where to place generated source files. The directory must already exist; \f3javac\fP will not create it. If a class is part of a package, the compiler puts the source file in a subdirectory reflecting the package name, creating directories as needed. For example, if you specify \f3\-s /home/mysrc\fP and the class is called \f2com.mypackage.MyClass\fP, then the source file will be placed in \f2/home/mysrc/com/mypackage/MyClass.java\fP.

.TP 3

\-source release

Specifies the version of source code accepted. The following values for \f2release\fP are allowed:

.RS 3

.TP 3

1.3

The compiler does \f2not\fP support assertions, generics, or other language features introduced after JDK 1.3.

.TP 3

1.4

The compiler accepts code containing assertions, which were introduced in JDK 1.4.

.TP 3

1.5

The compiler accepts code containing generics and other language features introduced in JDK 5.

.TP 3

5

Synonym for 1.5.

.TP 3

1.6

This is the default value. No language changes were introduced in Java SE 6. However, encoding errors in source files are now reported as errors, instead of warnings, as previously.

.TP 3

6

Synonym for 1.6.

.TP 3

1.7

The compiler accepts code with features introduced in JDK 7.

.TP 3

7

Synonym for 1.7.

.RE

.TP 3

\-sourcepath sourcepath

Specify the source code path to search for class or interface definitions. As with the user class path, source path entries are separated by colons (\f3:\fP) and can be directories, JAR archives, or ZIP archives. If packages are used, the local path name within the directory or archive must reflect the package name.

.br

.br

\f3Note:\fP Classes found through the class path may be subject to automatic recompilation if their sources are also found. See Searching For Types.

.TP 3

\-verbose

Verbose output. This includes information about each class loaded and each source file compiled.

.TP 3

\-version

Print version information.

.TP 3

\-Werror

Terminate compilation if warnings occur.

.TP 3

\-X

Display information about non\-standard options and exit.

.RE

.LP

.SS

Cross\-Compilation Options

.LP

.LP

By default, classes are compiled against the bootstrap and extension classes of the platform that \f3javac\fP shipped with. But \f3javac\fP also supports \f2cross\-compiling\fP, where classes are compiled against a bootstrap and extension classes of a different Java platform implementation. It is important to use \f3\-bootclasspath\fP and \f3\-extdirs\fP when cross\-compiling; see Cross\-Compilation Example below.

.LP

.RS 3

.TP 3

\-target version

Generate class files that target a specified version of the VM. Class files will run on the specified target and on later versions, but not on earlier versions of the VM. Valid targets are \f31.1\fP \f31.2\fP \f31.3\fP \f31.4\fP \f31.5\fP (also \f35\fP) \f31.6\fP (also \f36\fP) and \f31.7\fP (also \f37\fP).

.br

.br

The default for \f3\-target\fP depends on the value of \f3\-source\fP:

.RS 3

.TP 2

o

If \-source is \f3not specified\fP, the value of \-target is \f31.7\fP

.TP 2

o

If \-source is \f31.2\fP, the value of \-target is \f31.4\fP

.TP 2

o

If \-source is \f31.3\fP, the value of \-target is \f31.4\fP

.TP 2

o

For \f3all other values\fP of \-source, the value of \f3\-target\fP is the value of \f3\-source\fP.

.RE

.TP 3

\-bootclasspath bootclasspath

Cross\-compile against the specified set of boot classes. As with the user class path, boot class path entries are separated by colons (\f3:\fP) and can be directories, JAR archives, or ZIP archives.

.RE

.LP

.SS

Non\-Standard Options

.LP

.RS 3

.TP 3

\-Xbootclasspath/p:path

Prepend to the bootstrap class path.

.TP 3

\-Xbootclasspath/a:path

Append to the bootstrap class path.

.TP 3

\-Xbootclasspath/:path

Override location of bootstrap class files.

.TP 3

\-Xlint

Enable all recommended warnings. In this release, enabling all available warnings is recommended.

.TP 3

\-Xlint:all

Enable all recommended warnings. In this release, enabling all available warnings is recommended.

.TP 3

\-Xlint:none

Disable all warnings.

.TP 3

\-Xlint:name

Enable warning \f2name\fP. See the section Warnings That Can Be Enabled or Disabled with \-Xlint Option for a list of warnings you can enable with this option.

.TP 3

\-Xlint:\-name

Disable warning \f2name\fP. See the section Warnings That Can Be Enabled or Disabled with \-Xlint Option for a list of warnings you can disable with this option.

.TP 3

\-Xmaxerrs number

Set the maximum number of errors to print.

.TP 3

\-Xmaxwarns number

Set the maximum number of warnings to print.

.TP 3

\-Xstdout filename

Send compiler messages to the named file. By default, compiler messages go to \f2System.err\fP.

.TP 3

\-Xprefer:{newer,source}

Specify which file to read when both a source file and class file are found for a type. (See Searching For Types). If \f2\-Xprefer:newer\fP is used, it reads the newer of the source or class file for a type (default). If the \f2\-Xprefer:source\fP option is used, it reads source file. Use \f2\-Xprefer:source\fP when you want to be sure that any annotation processors can access annotations declared with a retention policy of \f2SOURCE\fP.

.TP 3

\-Xpkginfo:{always,legacy,nonempty}

Specify handling of package\-info files

.TP 3

\-Xprint

Print out textual representation of specified types for debugging purposes; perform neither annotation processing nor compilation. The format of the output may change.

.TP 3

\-XprintProcessorInfo

Print information about which annotations a processor is asked to process.

.TP 3

\-XprintRounds

Print information about initial and subsequent annotation processing rounds.

.RE

.LP

.SS

Warnings That Can Be Enabled or Disabled with \-Xlint Option

.LP

.LP

Enable warning \f2name\fP with the option \f3\-Xlint:\fP\f2name\fP, where \f2name\fP is one of the following warning names. Similarly, you can disable warning \f2name\fP with the option \f3\-Xlint:\-\fP\f2name\fP:

.LP

.RS 3

.TP 3

cast

Warn about unnecessary and redundant casts. For example:

.nf

\f3

.fl

String s = (String)"Hello!"

.fl

\fP

.fi

.TP 3

classfile

Warn about issues related to classfile contents.

.TP 3

deprecation

Warn about use of deprecated items. For example:

.nf

\f3

.fl

    java.util.Date myDate = new java.util.Date();

.fl

    int currentDay = myDate.getDay();

.fl

\fP

.fi

The method \f2java.util.Date.getDay\fP has been deprecated since JDK 1.1.

.TP 3

dep\-ann

Warn about items that are documented with an \f2@deprecated\fP Javadoc comment, but do not have a \f2@Deprecated\fP annotation. For example:

.nf

\f3

.fl

  /**

.fl

   * @deprecated As of Java SE 7, replaced by {@link #newMethod()}

.fl

   */

.fl

.fl

  public static void deprecatedMethood() { }

.fl

.fl

  public static void newMethod() { }

.fl

\fP

.fi

.TP 3

divzero

Warn about division by constant integer 0. For example:

.nf

\f3

.fl

    int divideByZero = 42 / 0;

.fl

\fP

.fi

.TP 3

empty

Warn about empty statements after \f2if\fP statements. For example:

.nf

\f3

.fl

class E {

.fl

    void m() {

.fl

        if (true) ;

.fl

    }

.fl

}

.fl

\fP

.fi

.TP 3

fallthrough

Check \f2switch\fP blocks for fall\-through cases and provide a warning message for any that are found. Fall\-through cases are cases in a \f2switch\fP block, other than the last case in the block, whose code does not include a \f2break\fP statement, allowing code execution to "fall through" from that case to the next case. For example, the code following the \f2case 1\fP label in this \f2switch\fP block does not end with a \f2break\fP statement:

.nf

\f3

.fl

switch (x) {

.fl

case 1:

.fl

       System.out.println("1");

.fl

       //  No break statement here.

.fl

case 2:

.fl

       System.out.println("2");

.fl

}

.fl

\fP

.fi

If the \f2\-Xlint:fallthrough\fP flag were used when compiling this code, the compiler would emit a warning about "possible fall\-through into case," along with the line number of the case in question.

.TP 3

finally

Warn about \f2finally\fP clauses that cannot complete normally. For example:

.nf

\f3

.fl

  public static int m() {

.fl

    try {

.fl

      throw new NullPointerException();

.fl

    } catch (NullPointerException e) {

.fl

      System.err.println("Caught NullPointerException.");

.fl

      return 1;

.fl

    } finally {

.fl

      return 0;

.fl

    }

.fl

  }

.fl

\fP

.fi

The compiler generates a warning for \f2finally\fP block in this example. When this method is called, it returns a value of \f20\fP, not \f21\fP. A \f2finally\fP block always executes when the \f2try\fP block exits. In this example, if control is transferred to the \f2catch\fP, then the method exits. However, the \f2finally\fP block must be executed, so it is executed, even though control has already been transferred outside the method.

.TP 3

options

Warn about issues relating to the use of command line options. See Cross\-Compilation Example for an example of this kind of warning.

.TP 3

overrides

Warn about issues regarding method overrides. For example, consider the following two classes:

.nf

\f3

.fl

public class ClassWithVarargsMethod {

.fl

  void varargsMethod(String... s) { }

.fl

}

.fl

\fP

.fi

.nf

\f3

.fl

public class ClassWithOverridingMethod extends ClassWithVarargsMethod {

.fl

  @Override

.fl

  void varargsMethod(String[] s) { }

.fl

}

.fl

\fP

.fi

The compiler generates a warning similar to the following:

.br

.br

\f2warning: [override] varargsMethod(String[]) in ClassWithOverridingMethod overrides varargsMethod(String...) in ClassWithVarargsMethod; overriding method is missing '...'\fP

.br

.br

When the compiler encounters a varargs method, it translates the varargs formal parameter into an array. In the method \f2ClassWithVarargsMethod.varargsMethod\fP, the compiler translates the varargs formal parameter \f2String... s\fP to the formal parameter \f2String[] s\fP, an array, which matches the formal parameter of the method \f2ClassWithOverridingMethod.varargsMethod\fP. Consequently, this example compiles.

.TP 3

path

Warn about invalid path elements and nonexistent path directories on the command line (with regards to the class path, the source path, and other paths). Such warnings cannot be suppressed with the \f2@SuppressWarnings\fP annotation. For example:

.nf

\f3

.fl

javac \-Xlint:path \-classpath /nonexistentpath Example.java

.fl

\fP

.fi

.TP 3

processing

Warn about issues regarding annotation processing. The compiler generates this warning if you have a class that has an annotation, and you use an annotation processor that cannot handle that type of exception. For example, the following is a simple annotation processor:

.br

.br

\f3Source file \fP\f4AnnoProc.java\fP:

.nf

\f3

.fl

import java.util.*;

.fl

import javax.annotation.processing.*;

.fl

import javax.lang.model.*;

.fl

import javax.lang.model.element.*;

.fl

.fl

@SupportedAnnotationTypes("NotAnno")

.fl

public class AnnoProc extends AbstractProcessor {