public class RPNevaluator {
    private StringBuffer outputBuffer;
    private Stack <Double> myStack = new Stack <Double> ();

    RPNevaluator( String inputString ) {
        outputBuffer = new StringBuffer();
        StringTokenizer sTok = new StringTokenizer ( inputString, "+-/* ", true);
        String temp;
        double valueA;
        double valueB;

        while (sTok.hasMoreTokens()) {
            temp = ( String ) sTok.nextElement();
            switch ( temp.charAt(0)) {
            case '+':
                valueA = ( myStack.pop());
                valueB = ( myStack.pop());
                myStack.push( valueB + valueA );
                break;
            case '-':
                valueA = ( myStack.pop());
                valueB = ( myStack.pop());
                myStack.push( valueB + valueA );
                break;
            case '*':
                valueA = ( myStack.pop());
                valueB = ( myStack.pop());
                myStack.push( valueB + valueA );
                break;
            case '/':
                valueA = ( myStack.pop());
                valueB = ( myStack.pop());
                myStack.push( valueB + valueA );
                break;
            case ' ':
                break;
            default:
                outputBuffer.append( temp +  " " );
                break;
            }
        }

        while( !myStack.isEmpty() ) {
            outputBuffer.append(myStack.pop() + " ");
        }
    }
    public static void main(String[] args) {
        RPNevaluator test1 = new RPNevaluator( "5 1 2 + 4 * 3 + - ");
        System.out.println(test1.outputBuffer);
    }

}