code: protected File createAarClassesJar() throws MojoExecutionException
      {
          final File obfuscatedJarFile = new File( obfuscatedJar );
          if ( obfuscatedJarFile.exists() )
          {
              attachJar( obfuscatedJarFile );
              return obfuscatedJarFile;
          }
  
          final File classesJar = new File( targetDirectory, finalName + ".aar.classes.jar" );
          try
          {
              JarArchiver jarArchiver = new JarArchiver();
              jarArchiver.setDestFile( classesJar );
              jarArchiver.addDirectory( projectOutputDirectory,
                      classesJarIncludes,
                      classesJarExcludes );
              jarArchiver.createArchive();
              attachJar( classesJar );
              return classesJar;
          }
          catch ( ArchiverException e )
          {
              throw new MojoExecutionException( "ArchiverException while creating ." + classesJar + " file.", e );
          }
          catch ( IOException e )
          {
              throw new MojoExecutionException( "IOException while creating ." + classesJar + " file.", e );
          }
  
      }
docs: Creates an appropriate aar/classes.jar that does not include R
  
  @return File which is the AAR classes jar.
  @throws MojoExecutionException