message: using StringBuilder instead of StringBuffer
diff: @@ -76,15 +76,15 @@ public final class IntSeries {
  @Override
  public String toString() {
  - StringBuffer arrayStr = new StringBuffer();
  - arrayStr.append("[ ");
  + StringBuilder sb = new StringBuilder();
  + sb.append("[ ");
  for (int i = 0; i < buffer.length; i++) {
  - arrayStr.append(buffer[i]);
  + sb.append(buffer[i]);
  if (i != buffer.length - 1) {
  - arrayStr.append(", ");
  + sb.append(", ");
  }
  }
  - arrayStr.append(" ]");
  - return "{ head: " + head + ", end: " + end + ", size: " + size() + ", buffer: " + arrayStr.toString() + " }";
  + sb.append(" ]");
  + return "{ head: " + head + ", end: " + end + ", size: " + size() + ", buffer: " + sb.toString() + " }";
  }
  }
  