use 'sorted' flag in indexOf

primitiveCollections/src/main/java/org/lucares/collections/IntList.java

@@ -566,12 +566,20 @@ public final class IntList implements Serializable, Cloneable {
 	 *             if offset is negative, or larger than the size of the list
 	 */
 	public int indexOf(final int value, final int offset) {
-		for (int i = offset; i < index; i++) {
-			if (data[i] == value) {
-				return i;
+
+		int result = -1;
+		if (sorted) {
+			final int insertionPoint = Arrays.binarySearch(data, offset, size(), value);
+			result = insertionPoint < 0 ? -1 : insertionPoint;
+		} else {
+			for (int i = offset; i < index; i++) {
+				if (data[i] == value) {
+					result = i;
+					break;
+				}
 			}
 		}
-		return -1;
+		return result;
 	}
 
 	@Override