> cd $JAVA_HOME/bin

> pwd

/Library/Java/JavaVirtualMachines/jdk1..0_75.jdk/Contents/Home/bin

> ls

appletviewer   javafxpackager jmc            native2ascii   servertool

apt            javah          jps            orbd           tnameserv

extcheck       javap          jrunscript     pack200        unpack200

idlj           jcmd           jsadebugd      policytool     wsgen

jar            jconsole       jstack         rmic           wsimport

jarsigner      jdb            jstat          rmid           xjc

java           jhat           jstatd         rmiregistry

javac          jinfo          jvisualvm      schemagen

javadoc        jmap           keytool        serialver
 

> javac -help

用法: javac <options> <source files>

其中, 可能的选项包括:

  -g                         生成所有调试信息

  -g:none                    不生成任何调试信息

  -g:{lines,vars,source}     只生成某些调试信息

  -nowarn                    不生成任何警告

  -verbose                   输出有关编译器正在执行的操作的消息

  -deprecation               输出使用已过时的 API 的源位置

  -classpath <路径>            指定查找用户类文件和注释处理程序的位置

  -cp <路径>                   指定查找用户类文件和注释处理程序的位置

  -sourcepath <路径>           指定查找输入源文件的位置

  -bootclasspath <路径>        覆盖引导类文件的位置

  -extdirs <目录>              覆盖所安装扩展的位置

  -endorseddirs <目录>         覆盖签名的标准路径的位置

  -proc:{none,only}          控制是否执行注释处理和/或编译。

  -processor <class1>[,<class2>,<class3>...] 要运行的注释处理程序的名称; 绕过默认的搜索进程

  -processorpath <路径>        指定查找注释处理程序的位置

  -d <目录>                    指定放置生成的类文件的位置

  -s <目录>                    指定放置生成的源文件的位置

  -implicit:{none,class}     指定是否为隐式引用文件生成类文件

  -encoding <编码>             指定源文件使用的字符编码

  -source <发行版>              提供与指定发行版的源兼容性

  -target <发行版>              生成特定 VM 版本的类文件

  -version                   版本信息

  -help                      输出标准选项的提要

  -A关键字[=值]                  传递给注释处理程序的选项

  -X                         输出非标准选项的提要

  -J<标记>                     直接将 <标记> 传递给运行时系统

  -Werror                    出现警告时终止编译

  @<文件名>                     从文件读取选项和文件名

> javac -X

  -Xlint                     启用建议的警告

  -Xlint:{all,cast,classfile,deprecation,dep-ann,divzero,empty,fallthrough,finally,options,overrides,path,processing,rawtypes,serial,static,try,unchecked,varargs,-cast,-classfile,-deprecation,-dep-ann,-divzero,-empty,-fallthrough,-finally,-options,-overrides,-path,-processing,-rawtypes,-serial,-static,-try,-unchecked,-varargs,none} 启用或禁用特定的警告

  -Xbootclasspath/p:<路径>     置于引导类路径之前

  -Xbootclasspath/a:<路径>     置于引导类路径之后

  -Xbootclasspath:<路径>       覆盖引导类文件的位置

  -Djava.ext.dirs=<目录>       覆盖所安装扩展的位置

  -Djava.endorsed.dirs=<目录>  覆盖签名的标准路径的位置

  -Xmaxerrs <编号>             设置要输出的错误的最大数目

  -Xmaxwarns <编号>            设置要输出的警告的最大数目

  -Xstdout <文件名>             重定向标准输出

  -Xprint                    输出指定类型的文本表示

  -XprintRounds              输出有关注释处理循环的信息

  -XprintProcessorInfo       输出有关请求处理程序处理哪些注释的信息

  -Xprefer:{source,newer}    指定读取文件, 当同时找到隐式编译类的源文件和类文件时

  -Xpkginfo:{always,legacy,nonempty} 指定 package-info 文件的处理

这些选项都是非标准选项, 如有更改, 恕不另行通知。

>man javac

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-.  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  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 .

               Synonym for 1.5.

             1.6

                No  language  changes  were  introduced in Java SE . However,

                encoding errors in source files are  now  reported  as  errors

                instead of warnings as in previous releases of Java SE.

               Synonym for 1.6.

             1.7

                This is the default value. The compiler accepts code with fea-

                tures introduced in Java SE .

               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 ), 1.6 (also ), and 1.7 (also ).

          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 . For example:

                 int divideByZero =  / ;

          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  label in this switch block does not end

             with a break statement:

             switch (x) {

             case :

                    System.out.println("");

                    //  No break statement here.

             case :

                    System.out.println("");

             }

             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 ;

                 } finally {

                   return ;

                 }

               }

             The  compiler generates a warning for finally block in this exam-

             ple. When this method is called, it returns a value of , not  .

             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=; 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