Questions tagged [java]

Java is a general-purpose computer programming language that is concurrent, class-based, object-oriented, and specifically designed to have as few implementation dependencies as possible.

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Unable to executive function of smart contract on android studio java file

I am trying to execute some functions of my deployed contract in Android Studio through a Java file. I have generated Java Wrapper files. However, when I run Android Studio, there is no data added to ...
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18 views

Cannot generate java wrapper class from contract

currently I am trying to generate a java wrapper contract from my smart contract. The command I use is as seen below : web3j truffle generate --javaTypes C:\Users\name\Documents\test\...
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Verifying ethereum message signatures with java

I am using web3j to verify message signatures but there are some false negative results. For example this signature should be right, but it seems like the address could not be recovered: final ...
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21 views

Ethereum account for HD Wallet key generated with xpub key only using bitcoinj

Accordingly to the BIP32/BIP44 specification recommendations I generating HD Wallet addresses using bitcoinj library (DeterministicKey instances) with the path like M/44'/60'/0'/0/0 using xpub key ...
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48 views

Listen to latest event emitted by smart contract with web3j API in JAVA

I'm having a smart contract: pragma solidity ^0.4.21; contract NodeServie{ event triggerEvent(address indexed _sender, string randomStr); function callEventFunc(string str) public{ ...
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Downloading Epirus and Java In Git Bash Terminal - Error Message “Unable to Access Jar File” (I'm Using Windows 7)

I tried downloading the web3j/epirus command line tool as stated on your website: https://github.com/syscoin/sysethereum-contracts But I keep getting the error message 'Unable to access jar file' It ...
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1answer
163 views

Attempting to transfer erc20 token, but keep encountering insufficient funds for gas * price + value

I'm attempting to transfer an erc20 token, but keep running into insufficiant funds for gas * price + value, regardles of how much eth I have, I also have an estimate function which returns a value ...
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1answer
24 views

How to reliably send transaction via web3j while connection is poor?

I use Transfer.sendFunds(Web3j, Credentials, BigDecimal, Convert.Unit) to transfer money. Usually I convert it to flowable. Flowable/RemoteCall completes when transaction is included in block (...
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Return parameters is not getting translated to java using web3j cli

When using newest version of solidity compiler "pragma" solidity ^0.6.9 The program compilation is successful. I'm just using this code Contract Counter{ unit public Variable_name; ...
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37 views

Ethereum address(generated) and ecrecover computed address is not matching

I created the Ethereum address by following the below steps . 1. Generated a public key(ECDSAsecp256k1) from HSM. 2. Generated a Keeccak256 hash of Q point of ECPublicKeyParameters ...
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where to host my Java web app to fully decentralised?

I need a idea to host my webapp to be on some secure distributed network. my client doesn't want to deployed on aws or gcp. he wants it to be on decentralised network p2p. Your suggestion and advice ...
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How to deploy my java web app on ipfs?

How to host my java web app onto decentrailsed network like ipfs as my web need a web server like tomcat to run and serve the dynamic content so how can i install tomcat on ipfs and push my war in it ...
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org.web3j 4.5.18 ethGetBalance get stuck

I'm using the following simple code in order to obtain the wallet balance: Credentials credentials = Credentials.create(privateKey); web3.ethGetBalance(credentials.getAddress(), ...
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24 views

How to get bytecode in Java (all programmatically)?

I am trying to generate a bytecode to deploy a contract to ethereum. I have included node.exe as resource and try to install solcjs programmatically in node, but unfortunately i am stuck. My current ...
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30 views

How to generate private key and ethereum address

How can i generate a private key and address using bouncycastle provider in java ?with that generated a private key can able sign the data and broadcast in the ethereum network.
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12 views

How to Convert Byte[] to r,s,v value in java

I am using HSM to sign the message which giving the output in the byte[] . How to convert the byte[] to r,s,v values.
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48 views

Web3j and Ganache stack underflow error

I'm experiencing the error "Error processing transaction request: VM Exception while processing transaction: stack underflow" basically with any contract. I'm using Ganache v2.1.2 and Web3j 4.5.15. ...
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1answer
106 views

Not able to add 'replayPastTransactionsFlowable' transaction logs result into an collection List object using Web3j java?

I'm trying to create an api where i have to provide transaction logs in json objects but im unable to add result of replayPastTransactionsFlowable into an collection object @GetMapping("/test") ...
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274 views

How to get Ethereum transaction list by address in java web3j quickly?

Im trying to fetch transaction logs from ganache using web3j library to send it as an api ,is there any way where i can get all transactions from ganache quickly? @GetMapping("/test") public List&...
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110 views

How to use gas price for faster transaction in erc20 transafer event?

I'm trying to provide a customised gas price for faster transaction ,how can achieve that ? Web3j web3 = Web3j.build(new HttpService("http://")); ERC20 javaToken = ERC20.load(contractAddress,...
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110 views

Not able to decode the input data from transaction using web3j (Java)

I am creating transactions using web3j and passing some private data in that transaction. The transaction is also getting mined . I have subscribed to the mined blocks, where I am fetching the ...
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1answer
252 views

How to decode InputValue of ethereum using java web3j

**I'm trying to decode the inputValue of an transaction using web3j without using any contract abi and wrapper class,Im loading the contract using its contract address ,is there any way/inbuilt ...
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2answers
245 views

Unable to invoke smart contract function from Web3j contract wrapper

I've been learning about interacting with smart contracts through Android and the Web3j framework but have run into an issue. I'm trying to mint an ERC721 token and send it to an address but it doesn'...
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1answer
41 views

how can i fetch all the tokens from ethereum network to my wallet ?using web3js(nodejs) or web3j(java)?

I'm trying to fetch all the available tokens from ethereum network into my android wallet but could not able to find an suitable solution other than web scrapping
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117 views

Curl Request Java - How To

I am looking to use some of the management admin API's found here: https://github.com/ethereum/go-ethereum/wiki/Management-APIs but unfortunately, the web3j library does not support the calls that I ...
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1answer
208 views

Not able to generate java wrapper class from solidity smart contract using truffle

I'm trying to generate java wrapper class of solidity smart contract using truffle but not getting wrapperclass.java file Here is an command which i've used to generate abi/Json of that contract ...
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1answer
623 views

How estimate GAS from a contract call with Web3j

I'm trying to estimate gas cost of a contract call, i need to send a string to a contract, but i need to see if i overtook the GAS limit. I'm trying like this: Transaction t = Transaction....
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1answer
102 views

Listen to Ethereum transactions

I need to listen ethereum transactions for current count of addresses using web3j. I know that I can use subscribe to get transactions, but how can I add some filter to listen a certain number of ...
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1answer
44 views

Cryptocurrency payments in Centralized Architecture

I'm new to cryptocurrency, so not sure if I'm asking the right question on this... I want to develop a game with traditional centralized client/server architecture, probably java application server, ...
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106 views

Extra mining fees added in etherbase account

1st scenario - I have set miner.setEtherbase(eth.accounts[1]) and gasPrize is 0. 1 coin Transaction - And done transaction from 0th account to one random account. I expect 0 mining fees will add ...
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1answer
188 views

org.web3j.protocol.exceptions.TransactionException: Transaction receipt was not generated after 600 seconds for transaction

I am sending a transaction through this code public String transferEthByPk(String amount, String toAddress, String privateKey, Web3j web3j) { BigDecimal value = new BigDecimal(amount); ...
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1answer
115 views

Could someone explain to me the use of the FastRawTransactionManager class?

int pollingInterval = 3000; FastRawTransactionManager fastRawTxMgr = new FastRawTransactionManager(web3j, credentials, new PollingTransactionReceiptProcessor(web3j, pollingInterval, 40)); From what I ...
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351 views

Transaction receipt was not generated after 600 seconds for transaction:

I am sending a transaction through this code: txhash = careercertificate .createCertificate(id, fecha, nombre, rutalumno, instituto, rutinstituto, titulo, totalhash, ...
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1answer
285 views

Can't connect Android app to Ganache using retrofit

I'm have deployed contracts on ethereum blockchain. I have ganache running on server I'm tring to connect to it from android with this code: private BlockChainService() { Retrofit retrofit =...
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102 views

Invalid OPCode on passing address parameter through Java wrapper on smart contract using Ganache

I have been facing this issue for some time and I realized there must be a problem with Ganache or maybe someone has any idea why it doesn't work. I have created a very simple contract as below, it ...
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2answers
535 views

Offline transaction signing with web3j?

I'd like to generate and sign a transaction offline and then send that transaction with a different account. I've found a few web3js sources and I've read the web3 documentation, but I haven't found ...
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1answer
44 views

Is it worthwhile to store my supply chain product data on the blockchain using a smart contract? [closed]

I'm currently developing an android app that uses the Web3j framework (Java) to interact with my private Ethereum blockchain (running on Ganache). The app is a supply chain tool that will let users ...
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2answers
297 views

Unable to make a transaction with Data using Java api ethSendRawTransaction

I am trying to make a transaction between two different accounts using Java. It works perfectly fine as long as I am not using "Data" parameter. My intent is not to call a smart contract but to make ...
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1answer
405 views

org.web3j.tx.exceptions.ContractCallException: Empty value (0x) returned from contract

Problem: org.web3j.tx.exceptions.ContractCallException: Empty value (0x) returned from contract The code is as follows.... My java: String owner = managedWalletLookup.getOwner(contractAddress).send(...
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1answer
1k views

How to change the nonce between transactions in web3j?

I have this line of code where it registers a transaction in blockchain. And I wanted to know how I can make the nonce different between the transactions? txhash = careercertificate ....
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2answers
156 views

java.lang.RuntimeException: Error processing transaction request: replacement transaction underpriced Output from Server

I am generating transactions in a contract I deployed in the Rinkeby network and the first 300 or 400 transactions had no errors and I received the txHash, but when I continued I got this following ...
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1answer
360 views

What does the get Status () method return with a pending state transaction?

If a transaction has a successful state it returns 0x1 but if the transaction has a failed state it returns 0x0. My questions is, what to return when the transaction has a pending status? public ...
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1answer
483 views

How to apply EthFilter to specific address?

In web3.js, we can apply event filter something like below: this.event = this.Contract.events.MyEvent({ filter: { address: "0xAccountAddress" }, }) In Web3J, it is translated to EthFilter ...
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0answers
50 views

How to do decoding with web3j?

I am looking for how to decode the input data of a transaction and what I have obtained up to now is in utf-8 and it gives me this data: "Ã;` Q ò  à                          ...
2
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1answer
198 views

Anyone with knowledge in org.web3j.abi.Type Decoder?

I am trying to decode a String with this code that I found but I have not been able to do it. String to = inputdata.substring(10, 74); String value = inputdata.substring(74, 138); Method refMethod = ...
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420 views

How to decode the input data in java?

I receive the input data as the image shows. And when I try to decode it with the method: String inputdata = null; Optional<Transaction> tx = web3.ethGetTransactionByHash(txHash).send()....
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1answer
807 views

Get the input data of a transaction with web3j

How can I retrieve transaction details (including the input data) from a txHash using Web3j? I tried the following method: public void buscarHhash(Web3j web3, String txHash) throws IOException { ...
2
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1answer
1k views

How can I get the TxReceipt of a transaction with web3j?

How can I get the status of a transaction through the TxHash with web3j. I tried it like this: public int getEstado(String trx) { try { JSONObject json = readJsonFromUrl("https://api....
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1answer
130 views

How to get the txHash of a transaction?

I have this method where I make a transaction to the network rinkeby, but to know how I can get the hash of the transaction made. I am using java with web3j, in addition to using infura to connect to ...
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2answers
375 views

Pass specific address in Web3J send method

How to pass specific address in send method in Web3J? For example, using web3 javascript library, we can pass from address like below. contract.someMethod().send({ from: this.props.accounts[0] }) ...