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javac(1)                                   Basic Tools                                   javac(1)

NAME
       javac - Reads Java class and interface definitions and compiles them into bytecode and
       class files.

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

       Arguments can be in any order:

       options
              Command-line options. See 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 list options and source files. The -J options are not
              allowed in these files. See Command-Line Argument Files.

DESCRIPTION
       The javac command reads class and interface definitions, written in the Java programming
       language, and compiles them into bytecode class files. The javac command 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, list the file names on the command line.

       o For a large number of source files, list the file names in a file that is separated by
         blanks or line breaks. Use the list file name preceded by an at sign (@) with the javac
         command.

       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 that
       combine the inner and outer class names, such as MyClass$MyInnerClass.class.

       Arrange source files in a directory tree that reflects their package tree. For example, if
       all of your source files are in /workspace, then put the source code for
       com.mysoft.mypack.MyClass 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 the -d option.

OPTIONS
       The compiler has a set of standard options that are supported on the current development
       environment. An additional set of nonstandard options are specific to the current virtual
       machine and compiler implementations and are subject to change in the future. Nonstandard
       options begin with the -X option.

       o See also Cross-Compilation Options

       o See also Nonstandard Options

   STANDARD OPTIONS
       -Akey[=value]
              Specifies options to pass to annotation processors. These options are not
              interpreted by javac directly, but are made available for use by individual
              processors. The key value should be one or more identifiers separated by a dot (.).

       -cp path or -classpath path
              Specifies where to find user class files, and (optionally) annotation 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, then
              the user class path is the current directory. See Setting the Class Path.

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

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

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

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

       -d directory
              Sets the destination directory for class files. The directory must already exist
              because javac does not create it. If a class is part of a package, then javac puts
              the class file in a subdirectory that reflects the package name and creates
              directories as needed.

              If you specify -d/home/myclasses and the class is called com.mypackage.MyClass,
              then the class file is /home/myclasses/com/mypackage/MyClass.class.

              If the -d option is not specified, then javac puts each class file in the same
              directory as the source file from which it was generated.

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

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

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

       -endorseddirs directories
              Overrides the location of the endorsed standards path.

       -extdirs directories
              Overrides the location of the ext directory. The directories variable is a colon-
              separated list of directories. Each JAR file in the specified directories is
              searched for class files. All JAR files found become part of the class path.

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

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

       -g:none
              Does not generate any debugging information.

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

              source Source file debugging information.

              lines  Line number debugging information.

              vars   Local variable debugging information.

       -help
              Prints a synopsis of standard options.

       -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, then the default
              is to automatically generate class files. In this case, the compiler issues a
              warning if any such class files are generated when also doing annotation
              processing. The warning is not issued when the -implicit option is set explicitly.
              See Searching for Types.

       -Joption
              Passes option to the Java Virtual Machine (JVM), where option is one of the options
              described on the reference page for the Java launcher. For example, -J-Xms48m sets
              the startup memory to 48 MB. See java(1).

              Note: The CLASSPATH, -classpath, -bootclasspath, and -extdirs options do not
              specify the classes used to run javac. Trying to customize the compiler
              implementation with these options and variables is risky and often does not
              accomplish what you want. If you must customize the complier implementation, then
              use the -J option to pass options through to the underlying Java launcher.

       -nowarn
              Disables warning messages. This option operates the same as the -Xlint:none option.

       -parameters
              Stores formal parameter names of constructors and methods in the generated class
              file so that the method java.lang.reflect.Executable.getParameters from the
              Reflection API can retrieve them.

       -proc: [none, only]
              Controls whether annotation processing and compilation are done. -proc:none means
              that compilation takes place without annotation processing. -proc:only means that
              only annotation processing 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
              Specifies where to find annotation processors. If this option is not used, then the
              class path is searched for processors.

       -s dir
              Specifies the directory where to place the generated source files. The directory
              must already exist because javac does not create it. If a class is part of a
              package, then the compiler puts the source file in a subdirectory that reflects the
              package name and creates directories as needed.

              If you specify -s /home/mysrc and the class is called com.mypackage.MyClass, then
              the source file is put in /home/mysrc/com/mypackage/MyClass.java.

       -source release
              Specifies the version of source code accepted. The following values 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 language 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 earlier
                     releases of Java Platform, Standard Edition.

              6      Synonym for 1.6.

              1.7    The compiler accepts code with features introduced in Java SE 7.

              7      Synonym for 1.7.

              1.8    This is the default value. The compiler accepts code with features
                     introduced in Java SE 8.

              8      Synonym for 1.8.

       -sourcepath sourcepath
              Specifies the source code path to search for class or interface definitions. As
              with the user class path, source path entries are separated by colons (:) on Oracle
              Solaris and semicolons on Windows and can be directories, JAR archives, or ZIP
              archives. If packages are used, then the local path name within the directory or
              archive must reflect the package name.

              Note: Classes found through the class path might be recompiled when their source
              files are also found. See Searching for Types.

       -verbose
              Uses verbose output, which includes information about each class loaded and each
              source file compiled.

       -version
              Prints release information.

       -werror
              Terminates compilation when warnings occur.

       -X
              Displays information about nonstandard options and exits.

   CROSS-COMPILATION OPTIONS
       By default, classes are compiled against the bootstrap and extension classes of the
       platform that javac shipped with. But javac also supports cross-compiling, where classes
       are compiled against a bootstrap and extension classes of a different Java platform
       implementation. It is important to use the -bootclasspath and -extdirs options when cross-
       compiling.

       -target version
              Generates class files that target a specified release of the virtual machine. Class
              files will run on the specified target and on later releases, but not on earlier
              releases of the JVM. Valid targets are 1.1, 1.2, 1.3, 1.4, 1.5 (also 5), 1.6 (also
              6), 1.7 (also 7), and 1.8 (also 8).

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

              o If the -source option is not specified, then the value of the -target option is
                1.8

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

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

              o If the -source option is 1.5, then the value of the -target option is 1.8

              o If the -source option is 1.6, then the value of the -target is option 1.8

              o If the -source option is 1.7, then the value of the -target is option 1.8

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

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

   COMPACT PROFILE OPTION
       Beginning with JDK 8, the javac compiler supports compact profiles. With compact profiles,
       applications that do not require the entire Java platform can be deployed and run with a
       smaller footprint. The compact profiles feature could be used to shorten the download time
       for applications from app stores. This feature makes for more compact deployment of Java
       applications that bundle the JRE. This feature is also useful in small devices.

       The supported profile values are compact1, compact2, and compact3. These are additive
       layers. Each higher-numbered compact profile contains all of the APIs in profiles with
       smaller number names.

       -profile
              When using compact profiles, this option specifies the profile name when compiling.
              For example:

              javac -profile compact1 Hello.java

              javac does not compile source code that uses any Java SE APIs that is not in the
              specified profile. Here is an example of the error message that results from
              attempting to compile such source code:

              cd jdk1.8.0/bin
              ./javac -profile compact1 Paint.java
              Paint.java:5: error: Applet is not available in profile 'compact1'
              import java.applet.Applet;

              In this example, you can correct the error by modifying the source to not use the
              Applet class. You could also correct the error by compiling without the -profile
              option. Then the compilation would be run against the full set of Java SE APIs.
              (None of the compact profiles include the Applet class.)

              An alternative way to compile with compact profiles is to use the -bootclasspath
              option to specify a path to an rt.jar file that specifies a profile's image. Using
              the -profile option instead does not require a profile image to be present on the
              system at compile time. This is useful when cross-compiling.

   NONSTANDARD OPTIONS
       -Xbootclasspath/p:path
              Adds a suffix to the bootstrap class path.

       -Xbootclasspath/a:path
              Adds a prefix to the bootstrap class path.

       -Xbootclasspath/:path
              Overrides the location of the bootstrap class files.

       -Xdoclint:[-]group [/access]
              Enables or disables specific groups of checks, where group is one of the following
              values: accessibility, syntax, reference, html or missing. For more information
              about these groups of checks see the -Xdoclint option of the javadoc command. The
              -Xdoclint option is disabled by default in the javac command.

              The variable access specifies the minimum visibility level of classes and members
              that the -Xdoclint option checks. It can have one of the following values (in order
              of most to least visible) : public, protected, package and private. For example,
              the following option checks classes and members (with all groups of checks) that
              have the access level protected and higher (which includes protected, package and
              public):

              -Xdoclint:all/protected

              The following option enables all groups of checks for all access levels, except it
              will not check for HTML errors for classes and members that have access level
              package and higher (which includes package and public):

              -Xdoclint:all,-html/package

       -Xdoclint:none
              Disables all groups of checks.

       -Xdoclint:all[/access]
              Enables all groups of checks.

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

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

       -Xlint:none
              Disables all warnings.

       -Xlint:name
              Disables warning name. See Enable or Disable Warnings with the -Xlint Option for a
              list of warnings you can disable with this option.

       -Xlint:-name
              Disables warning name. See Enable or Disable Warnings with the -Xlint Option with
              the -Xlint option to get a list of warnings that you can disable with this option.

       -Xmaxerrs number
              Sets the maximum number of errors to print.

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

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

       -Xprefer:[newer,source]
              Specifies which file to read when both a source file and class file are found for a
              type. (See Searching for Types). If the -Xprefer:newer option is used, then it
              reads the newer of the source or class file for a type (default). If the
              -Xprefer:source option is used, then it reads the 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]
              Control whether javac generates package-info.class files from package-info.java
              files. Possible mode arguments for this option include the following.

              always Always generate a package-info.class file for every package-info.java file.
                     This option may be useful if you use a build system such as Ant, which
                     checks that each .java file has a corresponding .class file.

              legacy Generate a package-info.class file only if package-info.java contains
                     annotations. Don't generate a package-info.class file if package-info.java
                     only contains comments.

                     Note: A package-info.class file might be generated but be empty if all the
                     annotations in the package-info.java file have RetentionPolicy.SOURCE.

              nonempty
                     Generate a package-info.class file only if package-info.java contains
                     annotations with RetentionPolicy.CLASS or RetentionPolicy.RUNTIME.

       -Xprint
              Prints a textual representation of specified types for debugging purposes. Perform
              neither annotation processing nor compilation. The format of the output could
              change.

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

       -XprintRounds
              Prints information about initial and subsequent annotation processing rounds.

ENABLE OR DISABLE WARNINGS WITH THE -XLINT OPTION
       Enable warning name with the -Xlint:name option, where name is one of the following
       warning names. Note that you can disable a warning with the -Xlint:-name: option.

       cast   Warns about unnecessary and redundant casts, for example:

              String s = (String) "Hello!"

       classfile
              Warns about issues related to class file contents.

       deprecation
              Warns about the 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
              Warns 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
              Warns about division by the constant integer 0, for example:

              int divideByZero = 42 / 0;

       empty  Warns about empty statements after ifstatements, for example:

              class E {
                  void m() {
                       if (true) ;
                  }
              }

       fallthrough
              Checks the switch blocks for fall-through cases and provides 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 option was used when compiling this code, then the
              compiler emits a warning about possible fall-through into case, with the line
              number of the case in question.

       finally
              Warns about finally clauses that cannot complete normally, for example:

              public static int m() {
                try {
                   throw new NullPointerException();
                }  catch (NullPointerException(); {
                   System.err.println("Caught NullPointerException.");
                   return 1;
                 } finally {
                   return 0;
                 }
                }

              The compiler generates a warning for the finally block in this example. When the
              int method is called, it returns a value of 0. A finally block executes when the
              try block exits. In this example, when control is transferred to the catch block,
              the int method exits. However, the finally block must execute, so it is executed,
              even though control was transferred outside the method.

       options
              Warns about issues that related to the use of command-line options. See Cross-
              Compilation Options.

       overrides
              Warns about issues regarding method overrides. For example, consider 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 ClassWithOverridingMethod
              overrides varargsMethod(String...) in ClassWithVarargsMethod; overriding
              method is missing '...'

              When the compiler encounters a varargs method, it translates the varargs formal
              parameter into an array. In the method ClassWithVarargsMethod.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
              ClassWithOverridingMethod.varargsMethod. Consequently, this example compiles.

       path   Warns about invalid path elements and nonexistent path directories on the command
              line (with regard 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 when you have a class that has an annotation, and you use an annotation
              processor that cannot handle that type of exception. For example, the following is
              a simple annotation processor:

              Source file AnnocProc.java:

              import java.util.*;
              import javax.annotation.processing.*;
              import javax.lang.model.*;
              import.javaz.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 following warning:

              warning: [processing] No processor claimed any of these annotations: Anno

              To resolve this issue, you can rename the annotation defined and used in the class
              AnnosWithoutProcessors from Anno to NotAnno.

       rawtypes
              Warns about unchecked operations on raw types. The following statement generates a
              rawtypes warning:

              void countElements(List l) { ... }

              The following example does not generate a rawtypes warning

              void countElements(List<?> l) { ... }

              List is a raw type. However, List<?> is an unbounded wildcard parameterized type.
              Because List is a parameterized interface, always specify its type argument. In
              this example, the List formal argument is specified with an unbounded wildcard (?)
              as its formal type parameter, which means that the countElements method can accept
              any instantiation of the List interface.

       Serial Warns 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 definition of
              serialVersionUID

              If a serializable class does not explicitly declare a field named serialVersionUID,
              then the serialization runtime environment calculates a default serialVersionUID
              value for that class based on various aspects of the class, as described in the
              Java Object Serialization 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 can vary depending on compiler implementations, and as a result, might
              cause an unexpected InvalidClassExceptions during deserialization. To guarantee a
              consistent serialVersionUID value across different Java compiler implementations, a
              serializable class must declare an explicit serialVersionUID value.

       static Warns about issues relating to the 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 follows:

              XLintStatic.m1();

              Alternately, you can remove the static keyword from the declaration of the method
              m1.

       try    Warns about issues relating to use of try blocks, including try-with-resources
              statements. For example, a warning is generated for the following statement because
              the resource ac declared in the try block is not used:

              try ( AutoCloseable ac = getResource() ) {    // do nothing}

       unchecked
              Gives more detail for unchecked conversion warnings that are mandated 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 ls command has the parameterized type List<String>. When the List referenced by
              l is assigned to ls, the compiler generates an unchecked warning. At compile time,
              the compiler and JVM cannot determine whether l refers to a List<String> type. In
              this case, l does not refer to a List<String> type. As a result, heap pollution
              occurs.

              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>. However, the compiler still allows this assignment. It must
              allow this assignment to preserve backward compatibility with releases 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
              Warns 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);
                  }
                }
              }

              Note: A non-reifiable type is a type whose type information is not fully available
              at runtime.

              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 programming 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, you can specify one or more files that 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 file names in any combination. The
       arguments within a file can be separated by spaces or new line characters. If a file name
       contains embedded spaces, then put the whole file name in double quotation marks.

       File Names within an argument file are relative to the current directory, not the location
       of the argument file. Wild cards (*) are not allowed in these lists (such as for
       specifying *.java). Use of the at sign (@) 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 the javac command, pass in the path and name of each argument file with the
       at sign (@) leading character. When the javac command encounters an argument beginning
       with the at sign (@), it expands the contents of that file into the argument list.

       Example 1 Single Argument 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 Example 2

       Example 2 Two Argument Files

       You can create two argument files: one for the javac options and the other for the source
       file names. Note that the following lists have no line-continuation characters.

       Create a file named options that contains the following:

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

       Create a file named classes that contains the following:

       MyClass1.java
       MyClass2.java
       MyClass3.java

       Then, run the javac command as follows:

       javac @options @classes

       Example 3 Argument Files with Paths

       The argument files can have paths, but any file names inside the files are relative to the
       current working directory (not path1 or path2):

       javac @path1/options @path2/classes

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

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

   HOW ANNOTATION PROCESSING WORKS
       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 no path is specified, then the user class path is used.
       Processors are located by means of service provider-configuration files named META-
       INF/services/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 explicitly, 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 processors to determine what annotations
       they process. When a match is found, the processor is called. A processor can claim the
       annotations it processes, in which case no further attempt is made to find any processors
       for those annotations. After all of the annotations are claimed, the compiler does not
       search for additional processors.

       If any processors generate new source files, then another round of annotation processing
       occurs: Any newly generated source files are scanned, and the annotations processed as
       before. Any processors called on previous rounds are also called 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 annotation processors
       are called one last time, to give them a chance to complete any remaining work. Finally,
       unless the -proc:only option is used, the compiler compiles the original and all generated
       source files.

   IMPLICITLY LOADED SOURCE FILES
       To compile a set of source files, the compiler might need to implicitly load additional
       source files. See Searching for Types. Such files are currently not subject to annotation
       processing. By default, the compiler gives a warning when annotation processing occurred
       and any implicitly loaded source files are compiled. The -implicit option provides a way
       to suppress the warning.

SEARCHING FOR TYPES
       To compile a source file, the compiler often needs information about a type, but the type
       definition is not in the source files specified 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 that provide information through inheritance.

       For example, when you create a subclass java.applet.Applet, you are also using the
       ancestor classes of Applet: java.awt.Panel, java.awt.Container, java.awt.Component, and
       java.lang.Object.

       When the compiler needs type information, it searches for a source file or class file that
       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 option.

       If you set the -sourcepath option, then 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 the
       -extdirs options. See Cross-Compilation Options.

       A successful type search may produce a class file, a source file, or both. If both are
       found, then you can use the -Xprefer option to instruct the compiler which to use. If
       newer is specified, then the compiler uses the newer of the two files. If source is
       specified, the compiler uses 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 the -Xprefer option, then the compiler reads the source file to get the
       information it needs. By default the compiler also compiles the source file. You can use
       the -implicit option to specify the behavior. If none is specified, then no class files
       are generated for the source file. If class is specified, then class files are generated
       for the source file.

       The compiler might not discover the need for some type information until after annotation
       processing completes. When the type information is found in a source file and no -implicit
       option is specified, the compiler gives a warning that the file is being compiled without
       being subject 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
       The javac command supports the new Java Compiler API defined by the classes and interfaces
       in the javax.tools package.

   EXAMPLE
       To compile as though providing command-line arguments, use the following syntax:

       JavaCompiler javac = ToolProvider.getSystemJavaCompiler();

       The example writes diagnostics to the standard output stream and returns the exit code
       that javac would give when called from the command line.

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

   OLD INTERFACE
       Note: This API is retained for backward compatibility only. All new code should use the
       newer Java Compiler API.

       The com.sun.tools.javac.Main class provides two static methods to call 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 typically be
       passed to the compiler.

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

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

       Note: All other classes and methods found in a package with names that start with
       com.sun.tools.javac (subpackages of com.sun.tools.javac) are strictly internal and subject
       to change at any time.

EXAMPLES
       Example 1 Compile a Simple Program

       This example shows how to compile the Hello.java source file in the greetings directory.
       The class defined in Hello.java is called greetings.Hello. The greetings directory is the
       package directory both for the source file and the class file and is underneath the
       current directory. This makes it possible to use the default user class path. It also
       makes it unnecessary to specify a separate destination directory with the -d option.

       The source code in 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]);
               }
           }
       }

       Compile greetings.Hello:

       javac greetings/Hello.java

       Run greetings.Hello:

       java greetings.Hello World Universe Everyone
       Hello World
       Hello Universe
       Hello Everyone

       Example 2 Compile Multiple Source Files

       This example compiles the Aloha.java, GutenTag.java, Hello.java, and Hi.java source files
       in the greetings package.

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

       Example 3 Specify a User Class Path

       After changing one of the source files in the previous example, recompile it:

       pwd
       /examples
       javac greetings/Hi.java

       Because greetings.Hi refers to other classes in the greetings package, the compiler needs
       to find these other classes. The previous example works because the default user class
       path is the directory that contains the package directory. If you want to recompile this
       file without concern for which directory you are in, then add the examples directory to
       the user class path by setting CLASSPATH. This example uses the -classpath option.

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

       If you change greetings.Hi to use a banner utility, then 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 the greetings package, the program needs access to the greetings
       package, and to the classes that the greetings classes use.

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

       Example 4 Separate Source Files and Class Files

       The following example uses javac to compile code that runs on JVM 1.7.

       javac -source 1.7 -target 1.7 -bootclasspath jdk1.7.0/lib/rt.jar \
       -extdirs "" OldCode.java

       The -source 1.7 option specifies that release 1.7 (or 7) of the Java programming language
       be used to compile OldCode.java. The option -target 1.7 option ensures that the generated
       class files are compatible with JVM 1.7. 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 version of the bootstrap
       classes (the rt.jar library). If not, then the compiler generates a warning:

       javac -source 1.7 OldCode.java
       warning: [options] bootstrap class path not set in conjunction with
       -source 1.7

       If you do not specify the correct version of bootstrap classes, then the compiler uses the
       old language rules (in this example, it uses version 1.7 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 7) because reference to nonexistent methods
       can get included.

       Example 5 Cross Compile

       This example uses javac to compile code that runs on JVM 1.7.

       javac -source 1.7 -target 1.7 -bootclasspath jdk1.7.0/lib/rt.jar \
                   -extdirs "" OldCode.java

       The-source 1.7 option specifies that release 1.7 (or 7) of the Java programming language
       to be used to compile OldCode.java. The -target 1.7 option ensures that the generated
       class files are compatible with JVM 1.7.

       You must specify the -bootclasspath option to specify the correct version of the bootstrap
       classes (the rt.jar library). If not, then the compiler generates a warning:

       javac -source 1.7 OldCode.java
       warning: [options] bootstrap class path not set in conjunction with -source 1.7

       If you do not specify the correct version of bootstrap classes, then the compiler uses the
       old language rules combined with the new bootstrap classes. This combination can result in
       class files that do not work on the older platform (in this case, Java SE 7) because
       reference to nonexistent methods can get included. In this example, the compiler uses
       release 1.7 of the Java programming language.

SEE ALSO
       o java(1)

       o jdb(1)

       o javah(1)

       o javadoc(1)

       o jar(1)

       o jdb(1)

JDK 8                                     03 March 2015                                  javac(1)

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