Spreadsheet calculate/evaluateOperator methods implemented.

Axel/src/de/hs_mannheim/informatik/spreadsheet/Spreadsheet.java

@@ -210,25 +210,62 @@ public class Spreadsheet {
 	 * @return The result calculated.
 	 */
 	private long calculate(String formula) throws ArithmeticException {
-		Matcher m = Pattern.compile("([A-Z][0-9]*)|[-\\+\\*/]|[0-9]*").matcher(formula);
+		Matcher m = Pattern.compile("([A-Z][0-9]*)|[-+*/]|[0-9]*").matcher(formula);
 
 		long res = 0;
+		long currentOperand = 0;
+		String currentOperator = "+";
+		boolean firstOperator = true;
 
-		// TODO implement
-
-		// uncomment the following to see an example how the elements of a formula can be accessed
-		while (m.find()) {        // m.find() must always be used before m.group()
+		while (m.find()) {
 			String s = m.group();
-			if (!s.isEmpty()) {
-				System.out.println(s);
+
+			if (s.matches(("[0-9]+")))
+				currentOperand = Long.parseLong(s);
+			else if ((s.matches("[A-Z][1-9]*") || s.matches("[A-Z][1-9]*+")) && get(s).isEmpty())
+				currentOperand = 0;
+			else if ((s.matches("[A-Z][1-9]*") || s.matches("[A-Z][1-9]*+"))) {
+				currentOperand = Long.parseLong(get(s));
+			} else {
+				if (!firstOperator) {
+					res = evaluateOperator(res, currentOperand, currentOperator);
+				} else {
+					res = currentOperand;
+					firstOperator = false;
+				}
+				currentOperator = s;
 			}
 		}
 
+		if (!firstOperator) {
+			res = evaluateOperator(res, currentOperand, currentOperator);
+		} else
+			res = currentOperand;
+
 		return res;
 	}
 
-	// -----
+	private long evaluateOperator(long res, long currentOperand, String currentOperator) {
+		switch (currentOperator) {
+			case "+":
+				res += currentOperand;
+				break;
+			case "-":
+				res -= currentOperand;
+				break;
+			case "*":
+				res *= currentOperand;
+				break;
+			case "/":
+				res /= currentOperand;
+				break;
+			default:
+				throw new IllegalArgumentException("Invalid operator: " + currentOperator);
+		}
+		return res;
+	}
 
+	///---
 	public String toString() {
 		StringBuilder sb = new StringBuilder();