验签排序问题

Map<String,String> params = new TreeMap<String, String>()

StringBuffer signData = new StringBuffer();
for (Entry<String, String> entry : params.entrySet()) {
signData.append(entry.getKey()).append("=").append(entry.getValue()).append("&");
}

String signDataStr = signData.substring(0, signData.length() - 1);