private static StringBuilder getStringBuilder() {
        StringBuilder result = THREAD_LOCAL.get();
        if (result == null) {
            result = new StringBuilder(MAX_STRING_BUILDER_SIZE);
            THREAD_LOCAL.set(result);
        }
        trimToMaxSize(result, MAX_STRING_BUILDER_SIZE);
        result.setLength(0);
        return result;
    }
Returns a {@code StringBuilder} that this Layout implementation can use to write the formatted log event to.

@return a {@code StringBuilder}
httpclient5/src/main/java/org/apache/hc/client5/http/impl/Wire.java