<dependency>
<groupId>org.web3j</groupId>
<artifactId>core</artifactId>
<version>4.8.7</version>
</dependency>
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.RemoteCall;
import org.web3j.protocol.core.methods.response.EthAccounts;
import org.web3j.protocol.http.HttpService;
import java.io.IOException;
import java.util.List;
public class EtherumConnectionExample {
public static void main(String[] args) {
String url = "https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID";
Web3j web3 = Web3j.build(new HttpService(url));
try {
EthAccounts ethAccounts = web3.ethAccounts().send();
List<String> accounts = ethAccounts.getAccounts();
System.out.println(accounts);
} catch (IOException e) {
e.printStackTrace();
}
}
}
import org.web3j.protocol.Web3j;
import org.web3j.protocol.core.RemoteCall;
import org.web3j.protocol.http.HttpService;
import org.web3j.tx.Contract;
import org.web3j.utils.Convert;
import java.math.BigDecimal;
import java.math.BigInteger;
public class SmartContractExample {
public static void main(String[] args) throws Exception {
String url = "https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID";
Web3j web3 = Web3j.build(new HttpService(url));
String contractAddress = "0xYourContractAddress";
String privateKey = "0xYourPrivateKey";
String abi = "YourContractABI";
MyContract contract = MyContract.load(contractAddress, web3, Credentials.create(privateKey), Contract.GAS_PRICE, Contract.GAS_LIMIT);
RemoteCall<BigInteger> result = contract.get();
BigInteger value = result.send();
System.out.println(value);
BigDecimal newValue = BigDecimal.valueOf(100);
RemoteCall<TransactionReceipt> transactionReceipt = contract.set(Convert.toWei(newValue, Convert.Unit.ETHER).toBigInteger());
TransactionReceipt receipt = transactionReceipt.send();
System.out.println(receipt);
}
}
