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javac(1)                                                                                            javac(1)



NAME
       javac - Java compiler

SYNOPSIS
       javac [ options ] [ sourcefiles ] [ @argfiles ]

PARAMETERS
       Arguments may be in any order.

       options        Command line options.

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

       @argfiles      One  or  more  files  that list source files.  The -J options are not allowed in these
                      files.

DESCRIPTION
       The javac tool reads class and interface definitions, written in the Java programming  language,  and
       compiles them into bytecode class files.

       There are two ways to pass source code file names to javac:

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

        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 javac command line, preceded by an @ character.

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

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

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

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

   Searching for Types
       When  compiling a source file, the compiler often needs information about a type whose definition did
       not appear in the source files given on the command line.  The compiler needs  type  information  for
       every  class  or  interface used, extended, or implemented in the source file.  This includes classes
       and interfaces not explicitly mentioned in the source file  but  which  provide  information  through
       inheritance.

       For  example,  when  you  subclass  java.applet.Applet, you are also using Applet's ancestor classes:
       java.awt.Panel, java.awt.Container, java.awt.Component, and java.awt.Object.

       When the compiler needs type information, it looks for a source file or class file which defines  the
       type.   The  compiler  searches  first in the bootstrap and extension classes, then in the user class
       path (which by default is the current directory).  The user class path  is  defined  by  setting  the
       CLASSPATH  environment  variable  or  by using the -classpath command line option.  (For details, see
       Setting the Class Path.)

       If you use the -sourcepath option, the compiler searches the indicated path for source files;  other-wise otherwise
       wise  the compiler searches the user class path both for class files and source files.  You can spec-ify specify
       ify different bootstrap or extension classes with the -bootclasspath and -extdirs options; see Cross-Compilation CrossCompilation
       Compilation Options below.

       A successful type search may produce a class file, a source file, or both.  Here is how javac handles
       each situation:

        Search produces a class file but no source file: javac uses the class file.

        Search produces a source file but no class file: javac  compiles  the  source  file  and  uses  the
         resulting class file.

        Search produces both a source file and a class file: javac determines whether the class file is out
         of date.  If the class file is out of date, javac recompiles the source file and uses  the  updated
         class file.  Otherwise, javac just uses the class file.

         By default, javac considers a class file out of date only if it is older than the source file.

       Note:  javac  can  silently compile source files not mentioned on the command line.  Use the -verbose
       option to trace automatic compilation.

OPTIONS
       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 implementation and are subject to change  in  the  future.   Non-standard
       options begin with -X.

   Standard Options
       -classpath classpath
              Sets  the  user  class path, overriding the user class path in the CLASSPATH environment vari-able. variable.
              able.  If neither CLASSPATH or -classpath is specified, the user class path  consists  of  the
              current directory.  See Setting the Class Path for more details.

              If  the  -sourcepath  option is not specified, the user class path is searched for both source
              files and class files.

       -Djava.ext.dirs=directories
              Override the location of installed extensions.

       -Djava.endorsed.dirs=directories
              Override the location of endorsed standards path.

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

              If -d is not specified, javac puts the class file in the same directory as the source file.

              Note: The directory specified by -d is not automatically added to your user class path.

       -deprecation
              Shows a description of each use or override of a deprecated member or class.  Without  -depre-cation, -deprecation,
              cation,  javac  shows  the  names  of  source files that use or override deprecated members or
              classes.  -deprecation is shorthand for -Xlint:deprecation.

       -encoding encoding
              Sets the source file encoding name, such as EUCJIS/SJIS/ISO8859-1/UTF8.  If -encoding  is  not
              specified, the platform default converter is used.

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

       -g:none
              Does not generate any debugging information.

       -g:keyword-list
              Generates only some kinds of debugging information, specified by a  comma  separated  list  of
              keywords. Valid keywords are:

              source    Source file debugging information

              lines     Line number debugging information

              vars      Local variable debugging information

       -help  Prints a synopsis of standard options.

       -nowarn
              Disables warning messages. This has the same meaning as -Xlint:none.

       -source release
              Enables  support  for  compiling  source code containing assertions.  The following values for
              release are allowed:

                 1.5  The compiler accepts code containing generics and other language  features  introduced
                      in JDK 1.5. The compiler defaults to the 1.5 behavior if the -source flag is not used.

                 5    Synonym for 1.5

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

                 1.3  The compiler does not support assertions, generics, or other language features  intro-duced introduced
                      duced after JDK 1.3.

       -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 (:) and can be  directories,  JAR  ar-chives, archives,
              chives,  or  ZIP  archives.  If packages are used, the local path name within the directory or
              archive must reflect the package name.

              Note: Classes found through the classpath are subject  to  automatic  recompilation  if  their
              sources are found.

       -verbose
              Verbose  output.   This includes information about each class loaded and each source file com-piled. compiled.
              piled.

       -X     Display information about non-standard options and exit.

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

       -target version
              Generates  class  files  that  will work on VMs with the specified version.  The default is to
              generate class files to be compatible with 1.2 VMs, with one exception. When the  -source  1.4
              option is used, the default target is 1.4.  The versions supported by javac are:

              1.1    Ensures that generated class files will be compatible with 1.1 and later.  VMs.

              1.2    Generates  class files that will run on 1.2 and later VMs, but will not run on 1.1 VMs.

              1.3    Generates class files that run on VMs in the Java 2 SDK, v1.3 and later, but  will  not
                     run on 1.1 or 1.2 VMs.

              1.4    Generates  class  files  that will run on VMs in JDK 1.4 and later, but will not run on
                     1.1, 1.2, or 1.3 VMs.

              1.5    Generate class files that are compatible only with JDK 1.5 VMs.

              5      Synonym for 1.5

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

       -cldc1.0
              Use to compile CLDC programs. The compiler generates stack maps making the use of the preveri-fier preverifier
              fier unnecessary.

       -extdirs directories
              Cross-compiles against the specified extension directories.  directories are a colon-separated
              list of directories.  Each JAR archive in the specified  directories  is  searched  for  class
              files.

   Non-Standard Options
       -Xbootclasspath/p:path
              Prepend to the bootstrap class path.

       --Xbootclasspath/a:path
              Append to the bootstrap class path.

       -Xbootclasspath/:path
              Override location of bootstrap class files.

       -Xlint Enable all recommended warnings. In this release, all available warnings are recommended.

       -Xlint:none
              Disable all warnings not mandated by the Java Language Specification.

       -Xlint:-xxx
              Disable warning xxx, where xxx is one of the warning names supported for -Xlint:xxx, below.

       -Xlint:unchecked
              Give  more  detail  for  unchecked  conversion warnings that are mandated by the Java Language
              Specification.

       -Xlint:path
              Warn about nonexistent path (classpath, sourcepath, etc) directories.

       -Xlint:serial
              Warn about missing serialVersionUID definitions on serializable classes.

       -Xlint:finally
              Warn about finally clauses that cannot complete normally.

       -Xlint:fallthrough
              Check switch blocks for fall-through cases and provide a warning  message  for  any  that  are
              found.  Fall-through cases are cases in a switch block, other than the last case in the block,
              whose code does not include a break statement, allowing code execution to "fall through"  from
              that  case  to  the next case. For example, the code following the case 1 label in this switch
              block does not contain a break statement:

              switch (x) {
              case 1:
                      System.out.println("1");
                      //  No  break;  statement here.
              case 2:
                      System.out.println("2");
              }

       If the -Xlint:fallthrough 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.

       -Xmaxerrors number
              Set the maximum number of errors to print.

       -Xmaxwarns number
              Set the maximum number of warnings to print.

       -Xstdout filename
              Send compiler messages to the named file.  By default, compiler messages go to System.err.

THE -J OPTION
       -Joption
              Pass  option  to  the  java launcher called by javac.  For example, -J-Xms48m sets the startup
              memory to 48 megabytes. Although it does not begin with -X, it is not a `standard  option'  of
              javac.  It is a common convention for -J to pass options to the underlying VM executing appli-cations applications
              cations written in Java.

       Note: CLASSPATH, -classpath, -bootclasspath, and -extdirs do not specify  the  classes  used  to  run
       javac.  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 -J option to pass through options to  the  underlying  java
       launcher.

COMMAND LINE ARGUMENT FILES
       To shorten or simplify the javac command line, you can specify one or more files that themselves con-tain contain
       tain arguments to the javac command. This enables you to create javac commands of any length  on  any
       operating system.

       An  argument  file  can include javac options and source filenames in any combination.  The arguments
       within a file can be space-separated or newline-separated.  Filenames within  an  argument  file  are
       relative  to  the  current  directory,  not the location of the argument file.  Wildcards (*) are not
       allowed in these lists (such as for specifying *.java).  Use of the @ character to recursively inter-pret interpret
       pret files is not supported.

       When  executing  javac, pass in the path and name of each argument file with the @ leading character.
       When javac encounters an argument beginning with the character @, it expands  the  contents  of  that
       file into the argument list.

   Example - Single Arg File
       You could use a single argument file named argfile to hold all javac arguments:

                % javac @argfile

       This argument file could contain the contents of both files shown in the next example.

   Example - Two Arg Files
       You  can  create  two  argument files -- one for the javac options and the other for the source file-names: filenames:
       names: (Notice the following lists have no line-continuation characters.)

       Create a file named options containing:

              -d classes
              -g
              -sourcepath /java/pubs/ws/1.3/src/share/classes

       Create a file named classes containing:

              MyClass1.java
              MyClass2.java
              MyClass3.java

       You would then run javac with:

              % javac @options @classes

   Example - Arg Files with Paths
       The argument files can have paths, but any filenames inside the files are  relative  to  the  current
       working directory (not path1 or path2):

              % javac @path1/options @path2/classes

EXAMPLES
   Compiling a Simple Program
       One  source file, Hello.java, defines a class called greetings.Hello.  The greetings directory is the
       package directory both for the source file and the class file and is off the current directory.  This
       allows us to use the default user class path. It also makes it unnecessary to specify a separate des-tination destination
       tination directory with -d.

          % ls
             greetings/
          % ls greetings
             Hello.java
          % cat greetings/Hello.java
             package greetings;

             public class Hello {
                  public static void main(String[] args) {
                     for (int i=0; i < args.length; i++) {
                         System.out.println("Hello " + args[i]);
                     }
                  }
             }
          % javac greetings/Hello.java
          % ls greetings
             Hello.class   Hello.java
          % java greetings.Hello World Universe Everyone
             Hello World
             Hello Universe
             Hello Everyone

   Compiling Multiple Source Files
       This example compiles all the source files in the package greetings.

          % ls
             greetings/
          % ls greetings
             Aloha.java     GutenTag.java     Hello.java      Hi.java
          % javac greetings/*.java
          % ls greetings
             Aloha.class    GutenTag.class    Hello.class     Hi.class
             Aloha.java     GutenTag.java     Hello.java      Hi.java

   Specifying a User Class Path
       Having changed one of the source files in the previous example, we recompile it:

          % pwd
             /examples
          % javac greetings/Hi.java

       Since the class greetings.Hi refers to other classes in the greetings package, the compiler needs  to
       find these other classes.  The example above works, because our default user class path happens to be
       the directory containing the package directory.  But suppose we want to recompile this file  and  not
       worry  about which directory we're in?  Then we need to add /examples to the user class path.  We can
       do this by setting CLASSPATH, but here we'll use the -classpath option.

          % javac -classpath /examples /examples/greetings/Hi.java

       If we change greetings.Hi again, to use a banner utility, that utility also needs  to  be  accessible
       through the user class path.

          % javac -classpath /examples:/lib/Banners.jar /examples/greetings/Hi.java

       To execute a class in greetings, we need access both to greetings and to the classes it uses.

          % java -classpath /examples:/lib/Banners.jar greetings.Hi

   Separating Source Files and Class Files
       It  often  makes  sense  to  keep source files and class files in separate directories, especially on
       large projects.  We use -d to indicate the separate class file destination.  Since the  source  files
       are not in the user class path, we use -sourcepath to help the compiler find them.

          % ls
             classes/  lib/      src/
          % ls src
             farewells/
          % ls src/farewells
             Base.java      GoodBye.java
          % ls lib
             Banners.jar
          % ls classes
          % javac -sourcepath src -classpath classes:lib/Banners.jar \
             src/farewells/GoodBye.java -d classes
          % ls classes
             farewells/
          % ls classes/farewells
             Base.class      GoodBye.class

       Note:  The compiler compiled src/farewells/Base.java, even though we didn't specify it on the command
       line.  To trace automatic compiles, use the -verbose option.

   Cross-Compilation Example
       Here we use javac to compile code that will run on a 1.4 VM.

          % javac -target 1.4 -bootclasspath jdk1.4.2/lib/classes.zip \
               -extdirs "" OldCode.java

       The -target 1.4 option ensures that the generated class files will be compatible with  1.4  VMs.   BY
       default, javac compiles for 1.5.

       The Java 2 SDk's javac would also by default compile against its own bootstrap classes, so we need to
       tell javac to compile against JDK 1.4 bootstrap classes instead.  We do this with -bootclasspath  and
       -extdirs.  Failing to do this might allow compilation against a Java 2 Platform API that would not be
       present on a 1.4 VM and would fail at runtime.

SEE ALSO
       jar(1), java(1), javadoc(1), javah(1), javap(1), jdb(1)

       See or search the Java web site for the following:

       The Java Extensions Mechanism @
                 http://java.sun.com/j2se/1.5/docs/guide/extensions/index.html




                                                05 March 2002                                       javac(1)

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