Java

public class PrefixEvaluator
{
   private final int MAX_SIZE = 60;
   private BufferedReader stdin;
   //private Vector<Fraction> FractionList = new Vector<Fraction>();
   private Stack evaluate = new Stack(MAX_SIZE);
   private boolean valid = true;
   private Object answer1 = new Object();
   
   void run() throws IOException
   {
      String toEval = stdin.readLine(); 

      while( toEval != null && valid )
      {
         Object op1 = new Object();
         Object op2 = new Object();
       
         int eqns = 1;    
         System.out.println( "Raw Expression " + eqns + " is: " + toEval );         
         ReverseTokenizer equation = new ReverseTokenizer( toEval, " ");
         String token = equation.nextToken();
         if( token.charAt(0) == '(')
         {
            evaluate.push( token );
         }
         else if ( token.charAt(0) == '+' || 
                   token.charAt(0) == '*' || 
                   token.charAt(0) == '-'   )
         {
            if( evaluate.isEmpty() )
               System.out.println( "Invalid Expression" );
            else
            {   
               op2 = evaluate.pop();
               op1 = evaluate.pop();
               if( token.equals("+"))
                  addition(op1, op2);
               else if( token.equals("-"))
                  subtract(op1, op2);
               else if( token.equals("*"))
                  multiply(op1, op2);
               else
                  System.out.println( "Invalid Expression" );
            }
            eqns++;
         }
        
         toEval = stdin.readLine();
      }
      answer1 = evaluate.pop();
   }

   public void addition( Object op1, Object op2)
   {
      Fraction operand1 = new Fraction();
      Fraction operand2 = new Fraction();
      Fraction addAns = new Fraction();
      Object answer = new Object();
      operand1 = (Fraction)op1;
      operand2 = (Fraction)op2;
      addAns = operand1.plus(operand2);
      answer = (Object)addAns;
      evaluate.push(answer);
   }

private static String arraySearch (String[] myArray)
	{
		
        Arrays.sort(myArray,String.CASE_INSENSITIVE_ORDER);
		String name="";
		int index = Arrays.binarySearch(myArray, "java");
		
		name = "Found Java at: " + index;
		return name;
	}