java erc20授权转账

ERC20是以太坊上的代币标准，Java可以通过以太坊的API（如web3j）来与以太坊进行交互，实现授权转账的代码如下：

1. 授权

//导入web3j相关的类
import org.web3j.abi.datatypes.Address;
import org.web3j.abi.datatypes.generated.Uint256;
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.DefaultBlockParameterName;
import org.web3j.protocol.core.methods.response.TransactionReceipt;
import org.web3j.tx.Contract;
import org.web3j.tx.ManagedTransaction;
import org.web3j.tx.TransactionManager;
import org.web3j.tx.gas.DefaultGasProvider;

//代币合约地址
String contractAddress = "0x12345...";
//代币转账地址
String fromAddress = "0xabcdef...";
//代币接收地址
String toAddress = "0x123456...";
//代币授权数量
BigInteger tokenAmount = BigInteger.valueOf(10000);

//创建web3j实例
Web3j web3j = Web3j.build(new HttpService("https://ropsten.infura.io/v3/your-project-id"));
//创建交易管理器
TransactionManager transactionManager = new RawTransactionManager(web3j, credentials);
//创建代币合约实例
ERC20Token contract = ERC20Token.load(contractAddress, web3j, transactionManager, DefaultGasProvider.GAS_PRICE, DefaultGasProvider.GAS_LIMIT);

//授权代币合约
TransactionReceipt approveReceipt = contract.approve(new Address(toAddress), new Uint256(tokenAmount)).send();

2. 转账

//代币转账数量
BigInteger transferAmount = BigInteger.valueOf(100);

//调用代币合约的transferFrom方法实现转账
TransactionReceipt transferReceipt = contract.transferFrom(new Address(fromAddress), new Address(toAddress), new Uint256(transferAmount)).send();

以上代码中，`ERC20Token`是自定义的Java类，用于与代币合约进行交互，需要根据代币合约的ABI文件生成。具体生成方法可以参考web3j的官方文档。