1. Extract Method, introduce explain value

2. QrSegmenetAdvanced.java
3. THis class had many function. So, declare more method.

java/src/main/java/io/nayuki/qrcodegen/QrSegmentAdvanced.java

@@ -133,22 +133,22 @@ public final class QrSegmentAdvanced {
 		
 		// Calculate costs using dynamic programming
 		for (int i = 0; i < codePoints.length; i++) {
-			int c = codePoints[i];
+			int cPoint = codePoints[i];
 			int[] curCosts = new int[numModes];
 			{  // Always extend a byte mode segment
-				curCosts[0] = prevCosts[0] + countUtf8Bytes(c) * 8 * 6;
+				curCosts[0] = prevCosts[0] + countUtf8Bytes(cPoint) * 8 * 6;
 				charModes[i][0] = modeTypes[0];
 			}
 			// Extend a segment if possible
-			if (QrSegment.ALPHANUMERIC_CHARSET.indexOf(c) != -1) {  // Is alphanumeric
+			if (is_alphanumeric(cPoint)) {  // Is alphanumeric
 				curCosts[1] = prevCosts[1] + 33;  // 5.5 bits per alphanumeric char
 				charModes[i][1] = modeTypes[1];
 			}
-			if ('0' <= c && c <= '9') {  // Is numeric
+			if (is_numeric(cPoint)) {  // Is numeric
 				curCosts[2] = prevCosts[2] + 20;  // 3.33 bits per digit
 				charModes[i][2] = modeTypes[2];
 			}
-			if (isKanji(c)) {
+			if (isKanji(cPoint)) {
 				curCosts[3] = prevCosts[3] + 78;  // 13 bits per Shift JIS char
 				charModes[i][3] = modeTypes[3];
 			}
@@ -157,7 +157,8 @@ public final class QrSegmentAdvanced {
 			for (int j = 0; j < numModes; j++) {  // To mode
 				for (int k = 0; k < numModes; k++) {  // From mode
 					int newCost = (curCosts[k] + 5) / 6 * 6 + headCosts[j];
-					if (charModes[i][k] != null && (charModes[i][j] == null || newCost < curCosts[j])) {
+					boolean is_notNull_or_lower = charModes[i][k] != null && (charModes[i][j] == null || newCost < curCosts[j]);
+					if (is_notNull_or_lower) {
 						curCosts[j] = newCost;
 						charModes[i][j] = modeTypes[k];
 					}
@@ -189,6 +190,16 @@ public final class QrSegmentAdvanced {
 		}
 		return result;
 	}
+
+
+	private static boolean is_numeric(int c) {
+		return '0' <= c && c <= '9';
+	}
+
+
+	private static boolean is_alphanumeric(int c) {
+		return QrSegment.ALPHANUMERIC_CHARSET.indexOf(c) != -1;
+	}
 	
 	
 	// Returns a new list of segments based on the given text and modes, such that