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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 Main
  43. {
  44.   private static Upn calc = new Upn();
  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.     throws Exception
  56.   {
  57.     Scanner scan;
  58.  
  59.     /* get first line only */
  60.     scan = new Scanner(src);
  61.     if (!scan.hasNextLine())
  62.     {
  63.       scan.close();
  64.       return false;
  65.     }
  66.     String line1 = scan.nextLine();
  67.     scan.close();
  68.  
  69.     /* parse first line */
  70.     scan = new Scanner(line1);
  71.     boolean err = false;
  72.     while(!err && scan.hasNext())
  73.     {
  74.       /* pass operand or operator to UpnCalculator */
  75.       if (scan.hasNextInt())
  76.         calc.addOperand(scan.nextInt());
  77.       else if (scan.hasNext())
  78.       {
  79.         String op = scan.next();
  80.         if (!calc.supportsOperator(op))
  81.           err = true;
  82.         else
  83.         {
  84.           /* catch exceptions */
  85.           try
  86.           {
  87.             calc.addOperator(op);
  88.           }
  89.           catch(Exception e)
  90.           {
  91.             System.out.println("?");
  92.           }
  93.         }
  94.       }
  95.       else
  96.         err = true;
  97.     }
  98.     scan.close();
  99.  
  100.     return !err;
  101.   }
  102.  
  103.   /**
  104.    * main method
  105.    *
  106.    * @param args not used
  107.    */
  108.   public static void main(String args[])
  109.   {
  110.     /* try-catch for the sake of safety */
  111.     try
  112.     {
  113.       /* dump RPN stack of everything was ok */
  114.       if (parse(System.in))
  115.         System.out.print(calc);
  116.       else
  117.         System.out.println("FALSCHE EINGABE");
  118.     }
  119.     catch(Throwable e)
  120.     {
  121.       System.out.println("FALSCHE EINGABE");
  122.     }
  123.   }
  124. }
  125.