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


				  16 Mar 2012			      javac(1)