/* Copyright (c) 2006, Sun Microsystems, Inc. * All rights reserved. *  * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: *  *     * Redistributions of source code must retain the above copyright notice, *       this list of conditions and the following disclaimer. *     * Redistributions in binary form must reproduce the above copyright *       notice, this list of conditions and the following disclaimer in the *       documentation and/or other materials provided with the distribution. *     * Neither the name of the Sun Microsystems, Inc. nor the names of its *       contributors may be used to endorse or promote products derived from *       this software without specific prior written permission. *  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF * THE POSSIBILITY OF SUCH DAMAGE. */This version of the GUI parsing example defines the GUI interaction asa JavaCC lexical specification where the characters are read from theGUI and there is an finite automaton (FA) built out of lexical statesthat have moves on these characters. In the grammar, theUSER_CHAR_STREAM option is set to true and the BUILD_PARSER option hasbeen set to false.  The event handler method stuffs the characters intoa buffer from which characters are returned to the lexical analyzer(by readChar). The whole system is invoked through Main.java.The point of this example is to illustrate:. A very detailed example of an FA simulation using lexical states  where every character moves the FA.. How a lexical analyzer can be used without a standard (JavaCC  generated) CharStream object.. How a lexical analyzer can be used without a parser.. The fact that input can come from entities that are not even streams  (a GUI in this example).. That GUI interaction can be modeled as a regular expression  specification.To run the calculator (which is what this example implements), do:	javacc CalcInput.jj	javac *.java	java MainHomework:   Simplify the grammar so that (["0"-"9"])* is treated as a single   entity for moving the FA.