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  1. /*
  2.  * Copyright (c) 2008, Manuel Mausz <manuel at mausz.at>
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions are met:
  7.  *     * Redistributions of source code must retain the above copyright
  8.  *       notice, this list of conditions and the following disclaimer.
  9.  *     * Redistributions in binary form must reproduce the above copyright
  10.  *       notice, this list of conditions and the following disclaimer in the
  11.  *       documentation and/or other materials provided with the distribution.
  12.  *     * Neither the name of the copyright holders nor the
  13.  *       names of its contributors may be used to endorse or promote products
  14.  *       derived from this software without specific prior written permission.
  15.  *
  16.  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17.  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18.  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19.  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20.  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  22.  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
  23.  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24.  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
  25.  * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  26.  * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  27.  * DAMAGE.
  28.  */
  29.  
  30. import java.util.Scanner;
  31.  
  32. /**
  33.  * Implements a simple RPN (UPN) Calculator
  34.  * - Parses the given input syntax
  35.  * - passes them to the RPN Calculator
  36.  * - and prints the specified (tho completely non-informative) error messages
  37.  *
  38.  * @version 1.0
  39.  * @author  Manuel Mausz (manuel at mausz.at)
  40.  * @author  http://manuel.mausz.at/
  41.  */
  42. class UpnApplication
  43. {
  44.   private static UpnCalculator calc = new UpnCalculator();
  45.  
  46.   /**
  47.    * read operands and operator from first line of src
  48.    * parses RPN syntax; only allows integers as operands
  49.    * prints "?" to stdout if calculations fails
  50.    *
  51.    * @param src input stream
  52.    * @return boolean true on success, false otherwise
  53.    */
  54.   private static boolean parse(java.io.InputStream src)
  55.   {
  56.     Scanner scan;
  57.  
  58.     /* get first line only */
  59.     scan = new Scanner(src);
  60.     if (!scan.hasNextLine())
  61.     {
  62.       scan.close();
  63.       return false;
  64.     }
  65.     String line1 = scan.nextLine();
  66.     scan.close();
  67.  
  68.     /* parse first line */
  69.     scan = new Scanner(line1);
  70.     boolean err = false;
  71.     while(!err && scan.hasNext())
  72.     {
  73.       /* pass operand or operator to UpnCalculator */
  74.       if (scan.hasNextInt())
  75.         calc.addOperand(scan.nextInt());
  76.       else if (scan.hasNext())
  77.       {
  78.         String op = scan.next();
  79.         if (!calc.supportsOperator(op))
  80.           err = true;
  81.         else if (!calc.addOperator(op))
  82.           System.out.println("?");
  83.       }
  84.       else
  85.         err = true;
  86.     }
  87.     scan.close();
  88.  
  89.     return !err;
  90.   }
  91.  
  92.   /**
  93.    * main method
  94.    *
  95.    * @param args not used
  96.    */
  97.   public static void main(String args[])
  98.   {
  99.     /* try-catch for the sake of safety */
  100.     try
  101.     {
  102.       /* dump RPN stack of everything was ok */
  103.       if (parse(System.in))
  104.         System.out.print(calc);
  105.       else
  106.         System.out.println("FALSCHE EINGABE");
  107.     }
  108.     catch(Throwable e)
  109.     {
  110.       System.out.println("FALSCHE EINGABE");
  111.     }
  112.   }
  113. }
  114.