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NewChain SDK for java

Get Started

RPC URL

TestNet URL:

private final static String rpcUrl = "https://rpc1.newchain.newtonproject.org/";

Get a Web3j Instance

Get a Web3j instance with a Web3jService instance, which needs a URL as the parameter:

Web3j web3 = Web3j.build(new HttpService(rpcUrl));

Get the chainId (net version)

Get chain ID with the Web3j instance:

NetVersion netVersion = web3.netVersion().send();
String chainIDStr = netVersion.getNetVersion();

Generate Keystore

Create a standard keystore:

String fileName = WalletUtils.generateNewWalletFile(
                "123qwe",
                new File("C:\\Files\\wallet"));

Parameters

  • password (String): The password for the keystore.
  • destinationDirectory (File): The destination directory for the keystore.

Return Values

Return a String value which is the name of the keystore. It`s in the following format:

UTC--2019-03-09T03-20-42.743000000Z--02d9bec4c13aecd197362adf92ed23b00a95d8ab.json

Load Keystore

Load an existing keystore:

Credentials credentials = WalletUtils.loadCredentials(
                "123qwe",
                "C:\\Files\\wallet\\UTC--2019-03-09T03-20-42.743000000Z--02d9bec4c13aecd197362adf92ed23b00a95d8ab.json");

Parameters

  • password(String): The password for the keystore.
  • source(String): The path of the keystore.

Return Values

Return an Credentials instance with keystore information.

Get original Address and Convert it into NEW Address

Get the address of the keystore with the Credentials instance:

String fromAddress = credentials.getAddress();

Convert the original format address into NEW format:

String fromAddressNEWFormat = AddressUtil.originalAddress2NewAddress(fromAddress, chainIDStr);

Parameters

  • originalAddress(String): The address in original format.
  • chainID(String): The chainID you get above.

Return Values

Return a String value which is the NEW format address.

See Also

Get Balance

Get balance of the keystore with the Web3j instance:

EthGetBalance balance = web3.ethGetBalance(fromAddress, DefaultBlockParameterName.LATEST).send();
BigInteger b = balance.getBalance();

Parameters

  • s(String): The address.
  • defaultBlockParameter(DefaultBlockParameter): Integer block number, or the string "latest", "earliest" or "pending". You should put into DefaultBlockParameterName.LATEST("latest").

Return Values

Returns the balance of the account of given address.

See Also

Get nonce

Get the transaction count(nonce) of the account:

EthGetTransactionCount ethGetTransactionCount = web3.ethGetTransactionCount(
                fromAddress, DefaultBlockParameterName.LATEST).send();
BigInteger nonce = ethGetTransactionCount.getTransactionCount();

Parameters

  • s(String): The address.
  • defaultBlockParameter(DefaultBlockParameter): Integer block number, or the string "latest", "earliest" or "pending". You should put into DefaultBlockParameterName.LATEST("latest").

Return Values

Return the nonce of the account of given address.

Convert NEW Address into original Address

String newAddress = "NEW17zJoq3eHwv3x7cJNgdmG73Limvv7TwQurB4";
String toAddress = AddressUtil.newAddress2originalAddress(newAddress);

//getChainID() return the chain ID in hex string
String addressChainID = AddressUtil.getChainID(newAddress);

Integer inputChainID = Integer.parseInt(addressChainID,16);
Integer chainID = Integer.parseInt(chainIDStr);

if(!inputChainID.equals(chainID)){
    System.out.println("Wrong address. Please check the address.");
    return;
}

Parameters

  • newAdderss(String): The address in NEW format.

Return Values

Return the original address.

See Also

Get gasPrice

EthGasPrice ethGasPrice = web3.ethGasPrice().send();
BigInteger gasPrice = ethGasPrice.getGasPrice();

Parameters

None

Return Values

Return the gasPrice.

Get GasLimit

Get gas limit with Web3j.ethEstimateGas() function.This won`t sent a transaction on block chain.

BigDecimal value = BigDecimal.valueOf(10);
Transaction tx = Transaction.createEtherTransaction(
            fromAddress, nonce, gasPrice, null, toAddress, Convert.toWei(value, Convert.Unit.ETHER).toBigInteger());
EthEstimateGas ethEstimateGas = web3.ethEstimateGas(tx).send();
BigInteger gasLimit = ethEstimateGas.getAmountUsed();

Parameters

The Transaction.createEtherTransaction() function has 6 parameters:

  • from(String): From address.
  • nonce(BigInteger): The nonce you get from chain above.
  • gasPrice(BigInteger): The gasPrice you get from chain above.
  • gasLimit(BigInteger): The value you ask for, put null in this position.
  • to(String): To address.
  • value(BigInteger): The value you want to transfer.

Return Values

Return the gasLimit.

Note

The value passed into Transaction.createEtherTransaction() is in format of ISSAC(WEI).

You can convert NEW(ETHER) into ISSAC(WEI):

Convert.toWei(value, Convert.Unit.ETHER);  // 10 NEW(ETHER)

Also you can convert ISSAC(WEI) into NEW(ETHER):

Convert.fromWei(value, Convert.Unit.ETHER);  // 10 ISSAC(WEI)

See Also

Create Transaction

RawTransaction rawTransaction = RawTransaction.createEtherTransaction(
                nonce, gasPrice, gasLimit, toAddress, Convert.toWei(value, Convert.Unit.ETHER).toBigInteger());

Parameters

  • nonce(BigInteger): The nonce.
  • gasPrice(BigInteger): The gasPrice.
  • gasLimit(BigInteger): The gasLimit.
  • to(String): To address.
  • value(BigInteger): The value.

Return Values

Return the RawTransaction instance.

Sign and Send Transaction

byte[] signedMessage = TransactionEncoder.signMessage(rawTransaction, Integer.parseInt(chainIDStr), credentials);
String hexValue = Numeric.toHexString(signedMessage);
EthSendTransaction ethSendTransaction = web3.ethSendRawTransaction(hexValue).send();

Paremeters

The TransactionEncoder.signMessage() function require 3 parameters:

  • rawTransaction(RawTransaction): The instance of RawTransaction.
  • chainId(int): The chainId.
  • credentials(Credentials): The instance of Credentials.

Return Values

Return the signed message in byte[].

Get Error

Response.Error error = ethSendTransaction.getError();

Parameters

None

Return Values

Return an instance of Response.Error. If there are no errors, the instance will be null.

Get Hash Value

Get transaction hash.

String hash = ethSendTransaction.getTransactionHash();

Parameters

None

Return Values

Return the String value of transaction hash.

Advanced usage

Change Password of Keystore

Code

import com.fasterxml.jackson.databind.ObjectMapper;
import org.web3j.crypto.CipherException;
import org.web3j.crypto.ECKeyPair;
import org.web3j.crypto.Wallet;
import org.web3j.crypto.WalletFile;

import java.io.File;
import java.io.IOException;
...
private static void updateKeyStorePassword(String password, ECKeyPair ecKeyPair, String filePath) throws CipherException, IOException {
        ObjectMapper objectMapper = new ObjectMapper();
        WalletFile walletFile = Wallet.createStandard(password, ecKeyPair);
        File destination = new File(filePath);
        objectMapper.writeValue(destination, walletFile);
    }
...

How to Use

String password = "password";    //Your <b>OLD</b> password

File file = new File("/your/keystore/path");    //Your <b>KEYSTORE</b> path
String filePath = file.getAbsolutePath();

Credentials credentials = WalletUtils.loadCredentials(password, file);  
ECKeyPair ecKeyPair = credentials.getEcKeyPair();

updateKeyStorePassword(password, ecKeyPair, filePath);

Parameters

String password, ECKeyPair ecKeyPair, File destinationDirectory, String fileName

  • password(String): The NEW password you want for the keystore.
  • ecKeyPair(ECKeyPair): The ECKeyPair instance got from CredenTtials.getEcKeyPair().
  • filePath(String)L: The absolute file path of your keystore.

Return Values

No return value.

Check Address

####Code

String addressChainID = AddressUtil.getChainID(newAddress);
Integer inputChainID = Integer.parseInt(addressChainID,16);
System.out.println("input ID : " + inputChainID);
Integer chainID = Integer.parseInt(chainIDStr);
System.out.println("chain ID : " + chainID);
if(!inputChainID.equals(chainID)){
      System.out.println("Wrong input address. Please check the address you input.");
      return;
}