private static void longArrayAppend(StringBuilder sbuf, long[] a) {
        sbuf.append('[');
        final int len = a.length;
        for (int i = 0; i < len; i++) {
            sbuf.append(a[i]);
            if (i != len - 1)
                sbuf.append(", ");
        }
        sbuf.append(']');
    }
Assumes that argArray only contains arguments with no throwable as last element.

@param messagePattern
@param argArray
slf4j-api/src/main/java/org/slf4j/helpers/MessageFormatter.java