javac(1)                    General Commands Manual                   javac(1)



Name
       javac - Java programming language compiler

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



       Arguments may be in any order.

          options
             Command-line options.

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

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

          @argfiles
             One or more files that lists options and  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.
       It can also process annotations in Java source files and classes.

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

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

          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 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).

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

   Standard Options
          -Akey[=value]
             Options  to  pass  to annotation processors. These are not inter-
             preted by javac directly, but are made available for use by indi-
             vidual  processors.  key  should be one or more identifiers sepa-
             rated by ".".

          -cp path or -classpath path
             Specify where to find user class files, and (optionally)  annota-
             tion  processors  and source files. This class path overrides the
             user class path in the CLASSPATH environment variable. If neither
             CLASSPATH,  -cp  nor -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 also searched for source files.
             If the -processorpath option is not specified, the class path  is
             also searched for annotation processors.

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

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

          -d directory
             Set the destination directory for class files. The directory must
             already exist; javac will not create it. 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 each class files in the same
             directory as the source file from which it was generated.
             Note: The directory specified by -d is not automatically added to
             your user class path.

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

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

          -endorseddirs directories
             Override the location of endorsed standards path.

          -extdirs directories
             Overrides the location of  the  ext  directory.  The  directories
             variable  is  a colon-separated list of directories. Each JAR ar-
             chive in the specified directories is searched for  class  files.
             All JAR archives found are automatically part of the class path.
             If  you  are cross-compiling (compiling classes against bootstrap
             and extension classes of a different  Java  platform  implementa-
             tion),  this  option  specifies  the directories that contain the
             extension classes. See Cross-Compilation Options for more  infor-
             mation.

          -g Generate all debugging information, including local variables. By
             default, only line number and source file information  is  gener-
             ated.

          -g:none
             Do not generate any debugging information.

          -g:{keyword list}
             Generate 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
             Print a synopsis of standard options.

          -implicit:{class,none}
             Controls the generation of  class  files  for  implicitly  loaded
             source   files.   To  automatically  generate  class  files,  use
             -implicit:class.  To  suppress   class   file   generation,   use
             -implicit:none.  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.

          -Joption
             Pass  option  to  the java launcher called by javac. For example,
             -J-Xms48m sets the startup memory to 48 megabytes. It is a common
             convention  for -J to pass options to the underlying VM executing
             applications written in Java.
             Note: CLASSPATH, -classpath, -bootclasspath, and -extdirs do  not
             specify  the  classes used to run javac. Fiddling with the imple-
             mentation 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.

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

          -proc: {none,only}
             Controls  whether  annotation  processing  and/or  compilation is
             done. -proc:none means that compilation takes place without anno-
             tation processing. -proc:only means that only annotation process-
             ing is done, without any subsequent compilation.

          -processor class1[,class2,class3...]
             Names of the annotation processors  to  run.  This  bypasses  the
             default discovery process.

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

          -s dir
             Specify the directory where to place generated source files.  The
             directory  must  already  exist;  javac  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  -s  /home/mysrc  and  the
             class  is called com.mypackage.MyClass, then the source file will
             be placed in /home/mysrc/com/mypackage/MyClass.java.

          -source release
             Specifies the version of source code accepted. The following val-
             ues for release are allowed:

             1.3
                The  compiler  does not support assertions, generics, or other
                language features introduced after Java SE 1.3.

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

             1.5
                The  compiler  accepts code containing generics and other lan-
                guage features introduced in Java SE 5.

             5  Synonym for 1.5.

             1.6
                No language changes were introduced in  Java  SE  6.  However,
                encoding  errors  in  source  files are now reported as errors
                instead of warnings as in previous releases of Java SE.

             6  Synonym for 1.6.

             1.7
                This is the default value. The compiler accepts code with fea-
                tures introduced in Java SE 7.

             7  Synonym for 1.7.

          -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 archives, 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  class path may be subject to
             automatic recompilation if their  sources  are  also  found.  See
             Searching For Types.

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

          -version
             Print version information.

          -Werror
             Terminate compilation if warnings occur.

          -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  platform that javac shipped with. But javac also sup-
       ports cross-compiling, where classes are compiled against  a  bootstrap
       and  extension  classes of a different Java platform implementation. It
       is important to use -bootclasspath and -extdirs  when  cross-compiling;
       see Cross-Compilation Example below.

          -target version
             Generate  class  files that target a specified version of the VM.
             Class files will run on the specified target and  on  later  ver-
             sions,  but  not on earlier versions of the VM. Valid targets are
             1.1, 1.2, 1.3, 1.4, 1.5 (also 5), 1.6 (also 6), and 1.7 (also 7).

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

             o If -source is not specified, the value of -target is 1.7

             o If -source is 1.2, the value of -target is 1.4

             o If -source is 1.3, the value of -target is 1.4

             o If -source is 1.5, the value of -target is 1.7

             o If -source is 1.6, the value of -target is 1.7

             o For all other values of -source, the value of  -target  is  the
               value of -source.

          -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 (:) and can be directories, JAR archives, or ZIP archives.


   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, enabling all
             available warnings is recommended.

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

          -Xlint:none
             Disable all warnings.

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

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

          -Xmaxerrs 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.

          -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 -Xpre-
             fer:newer is used, it reads the newer of the source or class file
             for  a  type (default). If the -Xprefer:source option is used, it
             reads source file. Use -Xprefer:source when you want to  be  sure
             that  any  annotation  processors can access annotations declared
             with a retention policy of SOURCE.

          -Xpkginfo:{always,legacy,nonempty}
             Specify handling of package-info files

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

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

          -XprintRounds
             Print  information  about  initial and subsequent annotation pro-
             cessing rounds.


   Warnings That Can Be Enabled or Disabled with -Xlint Option
       Enable warning name with the option -Xlint:name, where name is  one  of
       the  following  warning  names. Similarly, you can disable warning name
       with the option -Xlint:-name:

          cast
             Warn about unnecessary and redundant casts. For example:
             String s = (String)"Hello!"

          classfile
             Warn about issues related to classfile contents.

          deprecation
             Warn about use of deprecated items. For example:
                 java.util.Date myDate = new java.util.Date();
                 int currentDay = myDate.getDay();
             The method java.util.Date.getDay has been  deprecated  since  JDK
             1.1.

          dep-ann
             Warn  about items that are documented with an @deprecated Javadoc
             comment, but do not have a @Deprecated annotation. For example:
               /**
                * @deprecated As of Java SE 7, replaced by {@link #newMethod()}
                */

               public static void deprecatedMethood() { }

               public static void newMethod() { }

          divzero
             Warn about division by constant integer 0. For example:
                 int divideByZero = 42 / 0;

          empty
             Warn about empty statements after if statements. For example:
             class E {
                 void m() {
                     if (true) ;
                 }
             }

          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 end
             with 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.

          finally
             Warn  about  finally  clauses  that cannot complete normally. For
             example:
               public static int m() {
                 try {
                   throw new NullPointerException();
                 } catch (NullPointerException e) {
                   System.err.println("Caught NullPointerException.");
                   return 1;
                 } finally {
                   return 0;
                 }
               }
             The compiler generates a warning for finally block in this  exam-
             ple.  When this method is called, it returns a value of 0, not 1.
             A finally block always executes when the try block exits. In this
             example,  if control is transferred to the catch, then the method
             exits. However, the finally block must be executed, so it is exe-
             cuted,  even  though control has already been transferred outside
             the method.

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

          overrides
             Warn about issues regarding method overrides. For  example,  con-
             sider the following two classes:
             public class ClassWithVarargsMethod {
               void varargsMethod(String... s) { }
             }
             public class ClassWithOverridingMethod extends ClassWithVarargsMethod {
               @Override
               void varargsMethod(String[] s) { }
             }
             The compiler generates a warning similar to the following:
             warning:  [override] varargsMethod(String[]) in ClassWithOverrid-
             ingMethod  overrides   varargsMethod(String...)   in   ClassWith-
             VarargsMethod; overriding method is missing '...'
             When  the compiler encounters a varargs method, it translates the
             varargs formal parameter into an array. In the method  ClassWith-
             VarargsMethod.varargsMethod,  the compiler translates the varargs
             formal parameter String... s to the formal parameter String[]  s,
             an array, which matches the formal parameter of the method Class-
             WithOverridingMethod.varargsMethod.  Consequently,  this  example
             compiles.

          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 @SuppressWarnings annotation. For example:
             javac -Xlint:path -classpath /nonexistentpath Example.java

          processing
             Warn about issues regarding annotation processing.  The  compiler
             generates  this  warning  if you have a class that has an annota-
             tion, and you use an annotation processor that cannot handle that
             type of exception. For example, the following is a simple annota-
             tion processor:
             Source file AnnoProc.java:
             import java.util.*;
             import javax.annotation.processing.*;
             import javax.lang.model.*;
             import javax.lang.model.element.*;

             @SupportedAnnotationTypes("NotAnno")
             public class AnnoProc extends AbstractProcessor {
                 public boolean process(Set<? extends TypeElement> elems, RoundEnvironment renv) {
                     return true;
                 }

                 public SourceVersion getSupportedSourceVersion() {
                     return SourceVersion.latest();
                 }
             }
             Source file AnnosWithoutProcessors.java:
             @interface Anno { }

             @Anno
             class AnnosWithoutProcessors { }
             The following commands compile the annotation processor AnnoProc,
             then  run  this  annotation  processor  against  the  source file
             AnnosWithoutProcessors.java:
             % javac AnnoProc.java
             % javac -cp . -Xlint:processing -processor AnnoProc -proc:only AnnosWithoutProcessors.java
             When the compiler  runs  the  annotation  processor  against  the
             source file AnnosWithoutProcessors.java, it generates the follow-
             ing warning:
             warning: [processing] No processor claimed any of  these  annota-
             tions: Anno
             To  resolve this issue, you can rename the annotation defined and
             used in the class AnnosWithoutProcessors from Anno to NotAnno.

          rawtypes
             Warn about unchecked  operations  on  raw  types.  The  following
             statement generates a rawtypes warning:
             void countElements(List l) { ... }
             The following does not generate a rawtypes warning:
             void countElements(List<?> l) { ... }
             List  is  a  raw  type.  However, List<?> is a unbounded wildcard
             parameterized type. Because List is  a  parameterized  interface,
             you should always specify its type argument. In this example, the
             List formal argument is specified with a unbounded  wildcard  (?)
             as  its formal type parameter, which means that the countElements
             method can accept any instantiation of the List interface.

          serial
             Warn about missing serialVersionUID definitions  on  serializable
             classes. For example:
             public class PersistentTime implements Serializable
             {
               private Date time;

                public PersistentTime() {
                  time = Calendar.getInstance().getTime();
                }

                public Date getTime() {
                  return time;
                }
             }
             The compiler generates the following warning:
             warning:  [serial] serializable class PersistentTime has no defi-
             nition of serialVersionUID
             If a serializable class does not explicitly declare a field named
             serialVersionUID, then the serialization runtime will calculate a
             default serialVersionUID value for that class  based  on  various
             aspects  of the class, as described in the Java Object Serializa-
             tion Specification. However, it is strongly recommended that  all
             serializable  classes  explicitly declare serialVersionUID values
             because the default process of computing  serialVersionUID  vales
             is  highly  sensitive to class details that may vary depending on
             compiler implementations,  and  can  thus  result  in  unexpected
             InvalidClassExceptions   during  deserialization.  Therefore,  to
             guarantee a consistent serialVersionUID  value  across  different
             Java  compiler implementations, a serializable class must declare
             an explicit serialVersionUID value.

          static
             Warn about issues relating to use of statics. For example:
             class XLintStatic {
                 static void m1() { }
                 void m2() { this.m1(); }
             }
             The compiler generates the following warning:
             warning: [static] static method should be qualified by type name, XLintStatic, instead of by an expression
             To resolve this issue, you can call the static method m1 as  fol-
             lows:
             XLintStatic.m1();
             Alternatively,  you can remove the static keyword from the decla-
             ration of the method m1.

          try
             Warn about issues  relating  to  use  of  try  blocks,  including
             try-with-resources  statements.  For example, a warning is gener-
             ated for the following statement because the resource ac declared
             in the try statement is not used:
             try ( AutoCloseable ac = getResource() ) {
                 // do nothing
             }

          unchecked
             Give  more detail for unchecked conversion warnings that are man-
             dated by the Java Language Specification. For example:
                 List l = new ArrayList<Number>();
                 List<String> ls = l;       // unchecked warning
             During type erasure, the types ArrayList<Number> and List<String>
             become ArrayList and List, respectively.
             The variable ls has the parameterized type List<String>. When the
             List referenced by l is assigned to ls, the compiler generates an
             unchecked warning; the compiler is unable to determine at compile
             time, and moreover knows that the JVM will not be able to  deter-
             mine at runtime, if l refers to a List<String> type; it does not.
             Consequently, heap pollution occurs.
             In detail, a heap pollution situation occurs when the List object
             l, whose static type is List<Number>, is assigned to another List
             object, ls, that has a different static type, List<String>.  How-
             ever,  the  compiler  still allows this assignment. It must allow
             this assignment to preserve backwards compatibility with versions
             of Java SE that do not support generics. Because of type erasure,
             List<Number> and List<String> both become List. Consequently, the
             compiler  allows  the assignment of the object l, which has a raw
             type of List, to the object ls.

          varargs
             Warn about unsafe usages of variable arguments (varargs) methods,
             in  particular,  those  that contain non-reifiable arguments. For
             example:
             public class ArrayBuilder {
               public static <T> void addToList (List<T> listArg, T... elements) {
                 for (T x : elements) {
                   listArg.add(x);
                 }
               }
             }
             The compiler generates the following warning for  the  definition
             of the method ArrayBuilder.addToList:
             warning: [varargs] Possible heap pollution from parameterized vararg type T
             When  the compiler encounters a varargs method, it translates the
             varargs formal parameter into an array. However,  the  Java  pro-
             gramming  language  does  not  permit  the  creation of arrays of
             parameterized types. In the  method  ArrayBuilder.addToList,  the
             compiler translates the varargs formal parameter T... elements to
             the formal parameter T[] elements, an array. However, because  of
             type  erasure, the compiler converts the varargs formal parameter
             to Object[] elements. Consequently, there  is  a  possibility  of
             heap pollution.


COMMAND LINE ARGUMENT FILES
       To  shorten  or simplify the javac command line, you can specify one or
       more files that themselves  contain  arguments  to  the  javac  command
       (except  -J  options). 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 new-
       line-separated. If a filename contains embedded spaces, put  the  whole
       filename in double quotes.

       Filenames  within  an  argument file are relative to the current direc-
       tory, 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 interpret  files  is  not  supported.  The  -J
       options  are  not  supported  because  they are passed to the launcher,
       which does not support argument files.

       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 filenames: (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


ANNOTATION PROCESSING
       javac provides direct support for  annotation  processing,  superseding
       the need for the separate annotation processing tool, apt.

       The  API  for  annotation  processors  is  defined in the javax.annota-
       tion.processing and javax.lang.model packages and subpackages.

   Overview of annotation processing
       Unless annotation processing is disabled with  the  -proc:none  option,
       the compiler searches for any annotation processors that are available.
       The search path can be specified with the -processorpath option; if  it
       is  not  given,  the user class path is used. Processors are located by
       means  of  service  provider-configuration  files  named  META-INF/ser-
       vices/javax.annotation.processing.Processor  on  the  search path. Such
       files should contain the names of any annotation processors to be used,
       listed one per line. Alternatively, processors can be specified explic-
       itly, using the -processor option.

       After scanning the source files and classes  on  the  command  line  to
       determine  what  annotations are present, the compiler queries the pro-
       cessors to determine what annotations they process.  When  a  match  is
       found, the processor will be invoked. A processor may "claim" the anno-
       tations it processes, in which case no further attempt is made to  find
       any  processors  for  those annotations. Once all annotations have been
       claimed, the compiler does not look for additional processors.

       If any processors generate any new source files, another round of anno-
       tation  processing will occur: any newly generated source files will be
       scanned, and  the  annotations  processed  as  before.  Any  processors
       invoked  on  previous  rounds  will  also  be invoked on all subsequent
       rounds. This continues until no new source files are generated.

       After a round occurs where no new source files are generated, the anno-
       tation  processors will be invoked one last time, to give them a chance
       to complete  any  work  they  may  need  to  do.  Finally,  unless  the
       -proc:only  option  is used, the compiler will compile the original and
       all the generated source files.

   Implicitly loaded source files
       To compile a set of source files, the compiler may need  to  implicitly
       load additional source files. (See Searching For Types). Such files are
       currently not subject to annotation processing. By  default,  the  com-
       piler will give a warning if annotation processing has occurred and any
       implicitly loaded source files are compiled. See the  -implicit  option
       for ways to suppress the warning.

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.lang.Object.

       When the compiler needs type information, it looks for a source file or
       class  file  which  defines  the  type. The compiler searches for class
       files 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 set the -sourcepath option, the compiler searches the  indicated
       path  for  source files; otherwise the compiler searches the user class
       path for both class files and source files.

       You can specify different  bootstrap  or  extension  classes  with  the
       -bootclasspath  and  -extdirs  options;  see  Cross-Compilation Options
       below.

       A successful type search may produce a class file, a  source  file,  or
       both.  If  both  are found, you can use the -Xprefer option to instruct
       the compiler which to use. If newer is given, the compiler will use the
       newer  of  the  two  files.  If source is given, it will use the source
       file. The default is newer.

       If a type search finds a source file for a  required  type,  either  by
       itself,  or  as a result of the setting for -Xprefer, the compiler will
       read the source file to get the information it needs. In  addition,  it
       will  by  default  compile  the  source  file  as well. You can use the
       -implicit option to specify the behavior. If none is  given,  no  class
       files  will  be generated for the source file. If class is given, class
       files will be generated for the source file.

       The compiler may not discover the need for some type information  until
       after  annotation  processing  is  complete. If the type information is
       found in a source file and no -implicit option is given,  the  compiler
       will  give a warning that the file is being compiled without being sub-
       ject to annotation processing. To disable the warning,  either  specify
       the  file on the command line (so that it will be subject to annotation
       processing) or use the -implicit option to specify whether or not class
       files should be generated for such source files.

PROGRAMMATIC INTERFACE
       javac  supports  the  new  Java Compiler API defined by the classes and
       interfaces in the javax.tools package.

   Example
       To perform a compilation using arguments as you would give on the  com-
       mand line, you can use the following:

       JavaCompiler javac = ToolProvider.getSystemJavaCompiler();
       int rc = javac.run(null, null, null, args);


       This  will  write  any  diagnostics  to the standard output stream, and
       return the exit code that javac would give when invoked from  the  com-
       mand line.

       You  can use other methods on the javax.tools.JavaCompiler interface to
       handle diagnostics, control where files are read from and  written  to,
       and so on.

   Old Interface
       Note:  This  API  is retained for backwards compatibility only; all new
       code should use the Java Compiler API, described above.

       The com.sun.tools.javac.Main  class  provides  two  static  methods  to
       invoke the compiler from a program:

       public static int compile(String[] args);
       public static int compile(String[] args, PrintWriter out);


       The  args  parameter  represents any of the command line arguments that
       would normally be passed to the javac program and are outlined  in  the
       above Synopsis section.

       The  out  parameter indicates where the compiler's diagnostic output is
       directed.

       The return value is equivalent to the exit value from javac.

       Note that all other classes and methods found in a package  whose  name
       starts  with  com.sun.tools.javac  (informally known as sub-packages of
       com.sun.tools.javac) are strictly internal and subject to change at any
       time.

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 destination 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 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
       The following example uses javac to compile code that will run on a 1.6
       VM.

       % javac -source 1.6 -target 1.6 -bootclasspath jdk1.6.0/lib/rt.jar \
                   -extdirs "" OldCode.java


       The -source 1.6 option specifies that version 1.6 (or 6)  of  the  Java
       programming  language be used to compile OldCode.java. The option -tar-
       get 1.6 option ensures that the generated class files will be  compati-
       ble  with  1.6  VMs.  Note that in most cases, the value of the -target
       option is the value of the -source option; in  this  example,  you  can
       omit the -target option.

       You  must specify the -bootclasspath option to specify the correct ver-
       sion of the bootstrap classes (the rt.jar library). If  not,  the  com-
       piler generates a warning:

       % javac -source 1.6 OldCode.java
       warning: [options] bootstrap class path not set in conjunction with -source 1.6


       If  you  do  not  specify the correct version of bootstrap classes, the
       compiler will use the old language rules (in this example, it will  use
       version  1.6  of  the  Java programming language) combined with the new
       bootstrap classes, which can result in class files that do not work  on
       the  older  platform  (in  this  case,  Java SE 6) because reference to
       non-existent methods can get included.

SEE ALSO
          o The javac Guide @
            http://docs.oracle.com/javase/7/docs/tech-
            notes/guides/javac/index.html

          o java(1) - the Java Application Launcher

          o jdb(1) - Java Application Debugger

          o javah(1) - C Header and Stub File Generator

          o javap(1) - Class File Disassembler

          o javadoc(1) - API Documentation Generator

          o jar(1) - JAR Archive Tool

          o The Java Extensions Framework @
            http://docs.oracle.com/javase/7/docs/technotes/guides/exten-
            sions/index.html


                                  18 Jul 2013                         javac(1)
