The following changes to JFlex 1.4.3 have been done by JetBrains developers:

July 26, 2005:

 * JFlexTask.java: Added setCharAt() method for setting the -charat option from Ant
   builds.

July 8, 2005:

 * Main.java, Options.java, Emitter.java: Added new command line option -charat.
   The option replaces array index access when accessing the zzBufferL array with 
   calls to the .charAt() method.

December 21, 2009
 * Applied jflex-1.4.3-unicode-character-category.patch
 

October 1, 2012:
 * Merged pull request :
   Fix JFlex's Action.GENERAL_LOOK lookahead option to work with --charAt and --sliceandcharat.
   https://github.com/gshakhn/intellij-community/commit/e537a27e2bfc8e12500f00fa33e8e51ccaf47243