Is there a Java equivalent of estimateGas?

Question

I read from many questions (example: How to estimate the cost to call a Smart Contract method?) that web3.eth has a method estimateGas that can provide an estimate of the gas usage of a transaction/function call.

I am trying to get an estimate for calling a function using my Java wrapper class generated by the web3j CLI.

Web3j web3 = Web3j.build(new HttpService(endpoint));
Credentials creds = Credentials.create(privateKey);
DefaultGasProvider gasProvider = new DefaultGasProvider();
MyNFT contract = MyNFT.load(contractAddress, web3, creds, gasProvider);
// I am interested in estimating how much gas the following call will use
TransactionReceipt receipt = contract.mintNFT(recipient, tokenUri).send();

How should I go about doing this in Java? Is there a Java equivalent for estimateGas?

Answer 1

To estimate Gas Price :

public BigInteger estimateGas() throws IOException {

    EthGasPrice gas=web3j.ethGasPrice().send();
    return gas.getGasPrice();
}

Following code gives total gas used by LATEST block, so that is total is divided by the number of transactions, which gives you average Gas Limit of LATEST block on the chain.

To Estimate Gas Limit:

public BigInteger getGasLimit() throws IOException {
    EthBlock.Block block=web3j.ethGetBlockByNumber(DefaultBlockParameterName.LATEST, false).send().getBlock();
    return block.getGasLimit().divide(new BigInteger(String.valueOf(block.getTransactions().size())));
}

Final Total Gas:

gasPrice multiplied by Gas Limit