这里的不需要根据ascll码排序 直接加上换行就行

微信文档主要还是太乱了吧 网上找的很多都是v2的或者小程序的

```java

List<String> strings = new LinkedList<>();

strings.add(appId + "\n");

strings.add(timeStamp + "\n");

strings.add(nonceStr + "\n");

strings.add(pkg + "\n");

StringBuilder builder = new StringBuilder();

for (String string : strings) {

    builder.append(string);

}

PrivateKey rsa = PemUtil.loadPrivateKey(new ByteArrayInputStream(privateKey.getBytes(StandardCharsets.UTF_8)));

Sign sign = SecureUtil.sign(SignAlgorithm.SHA256withRSA);

sign.setPrivateKey(rsa);

byte[] signData = sign.sign(builder.toString().getBytes(StandardCharsets.UTF_8));

return Base64.encode(signData);

```

没有c#版的

https://wechatpay-api.gitbook.io/wechatpay-api-v3/qian-ming-zhi-nan-1/qian-ming-sheng-cheng

最下面有演示代码