/** If exists, reset and return, otherwise create, reset and return a writer. */
private static UTF8StreamWriter utf8StreamWriter() {
SoftReference<UTF8StreamWriter> ref = utf8StreamWriter.get();
UTF8StreamWriter writer = (ref == null) ? null : ref.get();
if (writer == null) {
writer = new UTF8StreamWriter(1024 * 4);
utf8StreamWriter.set(new SoftReference<>(writer));
}
writer.reset();
return writer;
}