public static String proxyTransferUSDTByPrivateKey(
            String from, String to,
            String value, String privateKey,
            String proxyAddr) {
        try {
            //加载转账所需的凭证，用私钥
            Credentials credentials = Credentials.create(privateKey);
            //获取nonce，交易笔数
            BigInteger nonce = getNonce(proxyAddr);
            BigInteger gasPrice = getGasPrice();
            BigInteger gasLimit =
                    Convert.toWei("2500000", Convert.Unit.WEI)
                            .toBigInteger(); // 最大手续费数量,差不多够转400U.如果到时转账慢了,可调大
            BigInteger bigInteger = Convert.toWei(value, Convert.Unit.ETHER).toBigInteger();
            //代币对象
            Function function = new Function(
                    "transferFrom",
                    Arrays.asList(new Address(from),
                            new Address(to),
                            new Uint256(bigInteger)),
                    Arrays.asList(new TypeReference<org.web3j.abi.datatypes.Type>() {
                    }));

            System.out.println("转账金额==>"+new BigInteger(value));
            String encodedFunction = FunctionEncoder.encode(function);
            RawTransaction rawTransaction = RawTransaction.createTransaction(nonce
                    , gasPrice
                    , gasLimit
                    , usdtAddr
                    , encodedFunction);
            //签名Transaction，这里要对交易做签名
            byte[] signMessage = TransactionEncoder.signMessage(rawTransaction, credentials);
            String hexValue = Numeric.toHexString(signMessage);
            //发送交易
            web3j = Web3j.build(new HttpService(web3jUrl));
            EthSendTransaction ethSendTransaction = web3j.ethSendRawTransaction(hexValue).sendAsync().get();
            if (Objects.nonNull(ethSendTransaction.getError())) {
                log.error(String.format("code: %s, message: %s", ethSendTransaction.getError().getCode(), ethSendTransaction.getError().getMessage()));
                throw new RuntimeException(String.format("code: %s, message: %s", ethSendTransaction.getError().getCode(), ethSendTransaction.getError().getMessage()));
            }
            return ethSendTransaction.getTransactionHash();
        } catch (Exception e) {
            throw new RuntimeException("转账ERC20 USDT失败." + e);
        }
    }