code: def generate(env):
      
      SCons.Tool.CreateJarBuilder(env)
  
      SCons.Tool.CreateJavaFileBuilder(env)
      SCons.Tool.CreateJavaClassFileBuilder(env)
      SCons.Tool.CreateJavaClassDirBuilder(env)
  
      env.AddMethod(Jar)
  
      env['JAR']        = 'jar'
      env['JARFLAGS']   = SCons.Util.CLVar('cf')
      env['_JARFLAGS']  = jarFlags
      env['_JARMANIFEST'] = jarManifest
      env['_JARSOURCES'] = jarSources
      env['_JARCOM']    = '$JAR $_JARFLAGS $TARGET $_JARMANIFEST $_JARSOURCES'
      env['JARCOM']     = "${TEMPFILE('$_JARCOM','$JARCOMSTR')}"
      env['JARSUFFIX']  = '.jar'
docs: Add Builders and construction variables for jar to an Environment.