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   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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  package jdkx.tools;
  
  import java.io.Writer;
  import java.nio.charset.Charset;
  import java.util.Locale;
  import java.util.concurrent.Callable;
  import jdkx.annotation.processing.Processor;
  
  /**
   * Interface to invoke Java programming language compilers from
   * programs.
   *
   * <p>The compiler might generate diagnostics during compilation (for
   * example, error messages).  If a diagnostic listener is provided,
   * the diagnostics will be supplied to the listener.  If no listener
   * is provided, the diagnostics will be formatted in an unspecified
   * format and written to the default output, which is {@code
   * System.err} unless otherwise specified.  Even if a diagnostic
   * listener is supplied, some diagnostics might not fit in a {@code
   * Diagnostic} and will be written to the default output.
   *
   * <p>A compiler tool has an associated standard file manager, which
   * is the file manager that is native to the tool (or built-in).  The
   * standard file manager can be obtained by calling {@linkplain
   * #getStandardFileManager getStandardFileManager}.
   *
   * <p>A compiler tool must function with any file manager as long as
   * any additional requirements as detailed in the methods below are
   * met.  If no file manager is provided, the compiler tool will use a
   * standard file manager such as the one returned by {@linkplain
   * #getStandardFileManager getStandardFileManager}.
   *
   * <p>An instance implementing this interface must conform to
   * <cite>The Java Language Specification</cite>
   * and generate class files conforming to
   * <cite>The Java Virtual Machine Specification</cite>.
   * The versions of these
   * specifications are defined in the {@linkplain Tool} interface.
   *
   * Additionally, an instance of this interface supporting {@link
   * jdkx.lang.model.SourceVersion#RELEASE_6 SourceVersion.RELEASE_6}
   * or higher must also support {@linkplain jdkx.annotation.processing
   * annotation processing}.
   *
   * <p>The compiler relies on two services: {@linkplain
   * DiagnosticListener diagnostic listener} and {@linkplain
   * JavaFileManager file manager}.  Although most classes and
   * interfaces in this package defines an API for compilers (and
   * tools in general) the interfaces {@linkplain DiagnosticListener},
   * {@linkplain JavaFileManager}, {@linkplain FileObject}, and
   * {@linkplain JavaFileObject} are not intended to be used in
   * applications.  Instead these interfaces are intended to be
   * implemented and used to provide customized services for a
   * compiler and thus defines an SPI for compilers.
   *
   * <p>There are a number of classes and interfaces in this package
   * which are designed to ease the implementation of the SPI to
   * customize the behavior of a compiler:
   *
   * <dl>
   *   <dt>{@link StandardJavaFileManager}</dt>
   *   <dd>
   *
   *     Every compiler which implements this interface provides a
   *     standard file manager for operating on regular {@linkplain
   *     java.io.File files}.  The StandardJavaFileManager interface
   *     defines additional methods for creating file objects from
   *     regular files.
   *
   *     <p>The standard file manager serves two purposes:
   *
   *     <ul>
   *       <li>basic building block for customizing how a compiler reads
   *       and writes files</li>
   *       <li>sharing between multiple compilation tasks</li>
   *     </ul>
   *
   *     <p>Reusing a file manager can potentially reduce overhead of
   *     scanning the file system and reading jar files.  Although there
   *     might be no reduction in overhead, a standard file manager must
   *     work with multiple sequential compilations making the following
   *     example a recommended coding pattern:
   *
   *     <pre>
   *       File[] files1 = ... ; // input for first compilation task
   *       File[] files2 = ... ; // input for second compilation task
   *
   *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
   *       StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);
   *
   *       {@code Iterable<? extends JavaFileObject>} compilationUnits1 =
   *           fileManager.getJavaFileObjectsFromFiles({@linkplain java.util.Arrays#asList Arrays.asList}(files1));
   *       compiler.getTask(null, fileManager, null, null, null, compilationUnits1).call();
   *
   *       {@code Iterable<? extends JavaFileObject>} compilationUnits2 =
   *           fileManager.getJavaFileObjects(files2); // use alternative method
   *       // reuse the same file manager to allow caching of jar files
   *       compiler.getTask(null, fileManager, null, null, null, compilationUnits2).call();
   *
   *       fileManager.close();</pre>
   *
   *   </dd>
   *
   *   <dt>{@link DiagnosticCollector}</dt>
   *   <dd>
   *     Used to collect diagnostics in a list, for example:
   *     <pre>
   *       {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;
   *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
   *       {@code DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();}
   *       StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null);
   *       compiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits).call();
   *
   *       for ({@code Diagnostic<? extends JavaFileObject>} diagnostic : diagnostics.getDiagnostics())
   *           System.out.format("Error on line %d in %s%n",
   *                             diagnostic.getLineNumber(),
   *                             diagnostic.getSource().toUri());
   *
   *       fileManager.close();</pre>
   *   </dd>
   *
   *   <dt>
   *     {@link ForwardingJavaFileManager}, {@link ForwardingFileObject}, and
   *     {@link ForwardingJavaFileObject}
   *   </dt>
   *   <dd>
   *
   *     Subclassing is not available for overriding the behavior of a
   *     standard file manager as it is created by calling a method on a
   *     compiler, not by invoking a constructor.  Instead forwarding
   *     (or delegation) should be used.  These classes makes it easy to
   *     forward most calls to a given file manager or file object while
   *     allowing customizing behavior.  For example, consider how to
   *     log all calls to {@linkplain JavaFileManager#flush}:
   *
   *     <pre>
   *       final  Logger logger = ...;
   *       {@code Iterable<? extends JavaFileObject>} compilationUnits = ...;
   *       JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
   *       StandardJavaFileManager stdFileManager = compiler.getStandardFileManager(null, null, null);
   *       JavaFileManager fileManager = new ForwardingJavaFileManager(stdFileManager) {
   *           public void flush() throws IOException {
   *               logger.entering(StandardJavaFileManager.class.getName(), "flush");
   *               super.flush();
   *               logger.exiting(StandardJavaFileManager.class.getName(), "flush");
   *           }
   *       };
   *       compiler.getTask(null, fileManager, null, null, null, compilationUnits).call();</pre>
   *   </dd>
   *
   *   <dt>{@link SimpleJavaFileObject}</dt>
   *   <dd>
   *
   *     This class provides a basic file object implementation which
   *     can be used as building block for creating file objects.  For
   *     example, here is how to define a file object which represent
   *     source code stored in a string:
   *
   *     <pre>
   *       /**
   *        * A file object used to represent source coming from a string.
   *        {@code *}/
   *       public class JavaSourceFromString extends SimpleJavaFileObject {
   *           /**
   *            * The source code of this "file".
   *            {@code *}/
   *           final String code;
   *
   *           /**
   *            * Constructs a new JavaSourceFromString.
   *            * {@code @}param name the name of the compilation unit represented by this file object
   *            * {@code @}param code the source code for the compilation unit represented by this file object
   *            {@code *}/
   *           JavaSourceFromString(String name, String code) {
   *               super({@linkplain java.net.URI#create URI.create}("string:///" + name.replace('.','/') + Kind.SOURCE.extension),
   *                     Kind.SOURCE);
   *               this.code = code;
   *           }
   *
   *           {@code @}Override
   *           public CharSequence getCharContent(boolean ignoreEncodingErrors) {
   *               return code;
   *           }
   *       }</pre>
   *   </dd>
   * </dl>
   *
   * @author Peter von der Ah&eacute;
   * @author Jonathan Gibbons
   * @see DiagnosticListener
   * @see Diagnostic
   * @see JavaFileManager
   * @since 1.6
   */
  public interface JavaCompiler extends Tool, OptionChecker {
  
      /**
       * Creates a future for a compilation task with the given
       * components and arguments.  The compilation might not have
       * completed as described in the CompilationTask interface.
       *
       * <p>If a file manager is provided, it must be able to handle all
       * locations defined in {@link StandardLocation}.
       *
       * <p>Note that annotation processing can process both the
       * compilation units of source code to be compiled, passed with
       * the {@code compilationUnits} parameter, as well as class
       * files, whose names are passed with the {@code classes}
       * parameter.
       *
       * @param out a Writer for additional output from the compiler;
       * use {@code System.err} if {@code null}
       * @param fileManager a file manager; if {@code null} use the
       * compiler's standard file manager
       * @param diagnosticListener a diagnostic listener; if {@code
       * null} use the compiler's default method for reporting
       * diagnostics
       * @param options compiler options, {@code null} means no options
       * @param classes names of classes to be processed by annotation
       * processing, {@code null} means no class names
       * @param compilationUnits the compilation units to compile, {@code
       * null} means no compilation units
       * @return an object representing the compilation
       * @throws RuntimeException if an unrecoverable error
       * occurred in a user supplied component.  The
       * {@linkplain Throwable#getCause() cause} will be the error in
       * user code.
       * @throws IllegalArgumentException if any of the options are invalid,
       * or if any of the given compilation units are of other kind than
       * {@linkplain JavaFileObject.Kind#SOURCE source}
       */
      CompilationTask getTask(Writer out,
                              JavaFileManager fileManager,
                              DiagnosticListener<? super JavaFileObject> diagnosticListener,
                              Iterable<String> options,
                              Iterable<String> classes,
                              Iterable<? extends JavaFileObject> compilationUnits);
  
      /**
       * Returns a new instance of the standard file manager implementation
       * for this tool.  The file manager will use the given diagnostic
       * listener for producing any non-fatal diagnostics.  Fatal errors
       * will be signaled with the appropriate exceptions.
       *
       * <p>The standard file manager will be automatically reopened if
       * it is accessed after calls to {@code flush} or {@code close}.
       * The standard file manager must be usable with other tools.
       *
       * @param diagnosticListener a diagnostic listener for non-fatal
       * diagnostics; if {@code null} use the compiler's default method
       * for reporting diagnostics
       * @param locale the locale to apply when formatting diagnostics;
       * {@code null} means the {@linkplain Locale#getDefault() default locale}.
       * @param charset the character set used for decoding bytes; if
       * {@code null} use the platform default
       * @return the standard file manager
       */
      StandardJavaFileManager getStandardFileManager(
          DiagnosticListener<? super JavaFileObject> diagnosticListener,
          Locale locale,
          Charset charset);
  
      /**
       * Interface representing a future for a compilation task.  The
       * compilation task has not yet started.  To start the task, call
       * the {@linkplain #call call} method.
       *
       * <p>Before calling the {@code call} method, additional aspects of the
       * task can be configured, for example, by calling the
       * {@linkplain #setProcessors setProcessors} method.
       */
      interface CompilationTask extends Callable<Boolean> {
          /**
           * Adds root modules to be taken into account during module
           * resolution.
           * Invalid module names may cause either
           * {@code IllegalArgumentException} to be thrown,
           * or diagnostics to be reported when the task is started.
           * @param moduleNames the names of the root modules
           * @throws IllegalArgumentException may be thrown for some
           *      invalid module names
           * @throws IllegalStateException if the task has started
           * @since 9
           */
          void addModules(Iterable<String> moduleNames);
  
          /**
           * Sets processors (for annotation processing).  This will
           * bypass the normal discovery mechanism.
           *
           * @param processors processors (for annotation processing)
           * @throws IllegalStateException if the task has started
           */
          void setProcessors(Iterable<? extends Processor> processors);
  
          /**
           * Sets the locale to be applied when formatting diagnostics and
           * other localized data.
           *
           * @param locale the locale to apply; {@code null} means apply no
           * locale
           * @throws IllegalStateException if the task has started
           */
          void setLocale(Locale locale);
  
          /**
           * Performs this compilation task.  The compilation may only
           * be performed once.  Subsequent calls to this method throw
           * {@code IllegalStateException}.
           *
           * @return true if and only all the files compiled without errors;
           * false otherwise
           *
           * @throws RuntimeException if an unrecoverable error occurred
           * in a user-supplied component.  The
           * {@linkplain Throwable#getCause() cause} will be the error
           * in user code.
           * @throws IllegalStateException if called more than once
           */
          @Override
          Boolean call();
      }
  }
  