production code refactored

TDD-pure-function/src/main/java/de/edu/hsfulda/ciip/tdd/BownlingCalculator.java

@@ -4,6 +4,10 @@ import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 public class BownlingCalculator {
+	private static final int SINGLE_DIGIT = 0;
+	private static final int STRIKE_SECOND_NEXT_THROW = 2;
+	private static final int STRIKE_NEXT_THROW = 1;
+	private static final String STRIKE = "X (\\d)(\\d)";
 	private static final int PINS_IN_FRAME = 10;
 	private static final String SPARE = "(\\d)/ (\\d)";
 	private static final String INCOMPLETE_FRAME = "\\d";
@@ -18,16 +22,23 @@ public class BownlingCalculator {
 
 	public int evaluate(String listOfThrows) {
 		int sum = 0;
-		sum += evaluateFrames(listOfThrows, INCOMPLETE_FRAME, m -> Integer.parseInt(m.group()));
-		sum += evaluateFrames(listOfThrows, SPARE, m -> PINS_IN_FRAME//
-				- Integer.parseInt(m.group(SPARE_FRAME_FIRST_THROW))
-				+ Integer.parseInt(m.group(SPARE_FRAME_FOLLOWING_THROW)));
-		sum += evaluateFrames(listOfThrows, "X (\\d)(\\d)", m -> PINS_IN_FRAME//
-				+ Integer.parseInt(m.group(1))
-				+ Integer.parseInt(m.group(2)));
+		sum += evaluateFrames(listOfThrows, INCOMPLETE_FRAME,
+				singleDigit -> convertMatchToInt(singleDigit, SINGLE_DIGIT));
+		sum += evaluateFrames(listOfThrows, SPARE, // trailing line comments for formatting
+				spare -> PINS_IN_FRAME //
+						- convertMatchToInt(spare, SPARE_FRAME_FIRST_THROW)
+						+ convertMatchToInt(spare, SPARE_FRAME_FOLLOWING_THROW));
+		sum += evaluateFrames(listOfThrows, STRIKE, //
+				strike -> PINS_IN_FRAME //
+						+ convertMatchToInt(strike, STRIKE_NEXT_THROW) //
+						+ convertMatchToInt(strike, STRIKE_SECOND_NEXT_THROW));
 		return sum;
 	}
 
+	private int convertMatchToInt(Matcher strike, int groupIndex) {
+		return Integer.parseInt(strike.group(groupIndex));
+	}
+
 	private int evaluateFrames(String listOfThrows, String frameStructurePattern, FrameCalculator frameCalculator) {
 		Matcher singleDigit = Pattern.compile(frameStructurePattern).matcher(listOfThrows);
 		int frameValue = 0;