Sample Solidity & Java Contracts

We have prepared some examples of various Solidity contracts to help you learn Jthereum faster.

Greeter Contract

This is a very basic contract that performs only 3 steps:

• It sets greeting on contract creation and allows to change it by the owner (creator of the contract) later.
• It returns greeting to everyone who calls sayHello method
• It returns Hello Daddy to the creator

We will look closely into this example to see how Jthereum works and what to expect when executing a contract like this one.

If you wanted to write this contract in Solidity it would look as following:

pragma solidity ^0.4.22;

contract Greeter {

    string greeting;

    address owner;

    modifier onlyOwner {
        require(isOwner(), "Only owner can do that!");
        _;
    }

    constructor(string _greeting) public {
        greeting = _greeting;

        owner = msg.sender;
    }

    function sayHello() public view returns(string) {
        if (isOwner()) {
            return "Hey daddy!";
        } else {
            return greeting;
        }
    }

    function setGreeting(string _newGreeting) public onlyOwner {
        greeting = _newGreeting;
    }

    function isOwner() view private returns(bool) {
        return msg.sender == owner;    
    }
}

And this is how it looks like in Java

package com.u7.jthereum.exampleContracts;

import com.u7.jthereum.annotations.*;
import com.u7.jthereum.types.*;

import static com.u7.jthereum.Jthereum.*;
import static com.u7.jthereum.SolidityStaticImports.*;

public class Greeter {
	String greeting = "Hi";
	Address owner;

	@View
	private void onlyOwner() {
		require(isOwner(), "Only owner can do that!");
	}

	public Greeter() {
		owner = msg.sender;
	}

	@View
	public String sayHello() {
                if (isOwner()) {
                    return "Hey daddy!";
                } else {
                    return greeting;
                }
	}

	public void setGreeting(String _newGreeting) {
		onlyOwner();

		greeting = _newGreeting;
	}

	@View
	private boolean isOwner() {
		return msg.sender.equals(owner);
	}

        // Compile, deploy, and call.
	public static void main(final String[] args) {
		compileAndDeploy();

		final Greeter a = createProxy(Greeter.class);

		p("message: " + a.sayHello());

		p("Setting new greeting");
		a.setGreeting("Hello from Java!");

		p("message: " + a.sayHello());
	}
}

What happens when we build and run the code? Well, Jthereum converts your Java code into the Solidity code. Take a look at it:

Compiling com.u7.jthereum.exampleContracts.Greeter

Solidity Source:

// Generated by Jthereum BETA version!
pragma solidity ^0.5.9;
contract Greeter
{
	string private greeting = "Hi";
	address private owner;
	function onlyOwner() private view 
	{
		require(isOwner(), "Only owner can do that!");
	}
	constructor() public 
	{
		owner = msg.sender;
	}
	function sayHello() public view returns (string memory) 
	{
		if (isOwner()) 
		{
			return "Hey daddy!";
		} else 
		{
			return greeting;
		}
	}
	function setGreeting(string memory _newGreeting) public 
	{
		onlyOwner();
		greeting = _newGreeting;
	}
	function isOwner() private view returns (bool) 
	{
		return (msg.sender == owner);
	}

}

Then your Solidity code is being compiled and deployed on the Blockchain. In this case we specified the blockchain to be “test”. Take a look at the output:

Argument values for call to Jthereum.compileAndDeploy(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = com.u7.jthereum.exampleContracts.Greeter.class;			// call stack (when called from ‘main()’ method on class to be deployed)
	String blockchainName = "test";								// global property: DEFAULT_BLOCKCHAIN
	String web3jURL = "http://test.jthereum.com:8545";					// global property: TEST_Web3j_URL
	BigInteger privateKey = pk for address: 0x572ba8f2a93abab1555981ce8f6bb3320a5b230b;	// global property: TEST_PrivateKey
	BigInteger gasPrice = 1;								// default gas price for 'test' blockchain
	BigInteger gasLimit = 7,999,999;							// default gas limit for 'test' blockchain


Deploying contract to the blockchain

Tx hash: 0xe3a539dbe871ea41e88313b12c81a7185f5307a12f571e601f68bfd93fb22b50
Waiting for transaction to be mined.
Your contract was deployed in block #2,823,106
The new contract address is at: 0x206c46ac16a5447e69539d1a1841663bb8dcf693 

Now argument values for Jthereum Proxy:

Argument values for call to Jthereum.createProxy(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = com.u7.jthereum.exampleContracts.Greeter.class;			// directly supplied
	String blockchainName = "test";								// most recent deployment for class Greeter
	String web3jURL = "http://test.jthereum.com:8545";					// global property: TEST_Web3j_URL
	String address = "0x206c46ac16a5447e69539d1a1841663bb8dcf693";				// most recent deployment to the blockchain 'test' for class Greeter
	BigInteger privateKey = pk for address: 0x572ba8f2a93abab1555981ce8f6bb3320a5b230b;	// global property: TEST_PrivateKey

Finally, here is our output result:

Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = com.u7.jthereum.exampleContracts.Greeter.class;			// inherited from Proxy Object configuration
	String blockchainName = "test";								// inherited from Proxy Object configuration
	String web3jURL = "http://test.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0x206c46ac16a5447e69539d1a1841663bb8dcf693";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0x572ba8f2a93abab1555981ce8f6bb3320a5b230b;	// inherited from Proxy Object configuration


Calling sayHello:
message: Hey daddy!
Setting new greeting

Argument values for call to ContractProxyContextInfo.callContractTransaction(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = com.u7.jthereum.exampleContracts.Greeter.class;			// inherited from Proxy Object configuration
	String blockchainName = "test";								// inherited from Proxy Object configuration
	String web3jURL = "http://test.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0x206c46ac16a5447e69539d1a1841663bb8dcf693";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0x572ba8f2a93abab1555981ce8f6bb3320a5b230b;	// inherited from Proxy Object configuration
	BigInteger gasPrice = 1;								// default gas price for 'test' blockchain
	BigInteger gasLimit = 7,999,999;							// default gas limit for 'test' blockchain


Calling setGreeting:

Tx hash: 0x85087866572b0ca1aa35245b87a95f4c4789e2b35552fbf63db323a717061bf2
Waiting for transaction to be mined.
Gas Used: 22,808
Total WEI used: 22,808
Total ETH used: 0.000000
(Gas Price: 1 wei)
Transaction succeeded with status: 0x1


Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = com.u7.jthereum.exampleContracts.Greeter.class;			// inherited from Proxy Object configuration
	String blockchainName = "test";								// inherited from Proxy Object configuration
	String web3jURL = "http://test.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0x206c46ac16a5447e69539d1a1841663bb8dcf693";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0x572ba8f2a93abab1555981ce8f6bb3320a5b230b;	// inherited from Proxy Object configuration


Calling sayHello:
message: Hello from Java!

Process finished with exit code 0

Basic Token Contract

On the Ethereum blockchain everyone can create a token. So why don’t we create one? This contract creates a token with various different options:

• It sets the intial supply of tokens on creation
• The contract creator gets initial tokens
• Tokens can be transferred to any account
• It sets a protection from overflow
• It sets an option for everyone to check balances

If you wanted to write this contract in Solidity it would look as following:

pragma solidity ^0.4.22;

contract BasicToken {
    uint public initialSupply;

    mapping(address=>uint) balances;
    
    constructor(uint _initialSupply) public {
        initialSupply = _initialSupply;
        balances[msg.sender] = _initialSupply;
    }
    
    function transfer(address _recipient, uint _amount) public {
        require(balances[msg.sender] >= _amount, "Not enough funds");
        require(_recipient != msg.sender, "No need to send tokens to yourself");
        require(balances[_recipient] + _amount > balances[_recipient]); //overflow check
        balances[msg.sender] -= _amount;
        balances[_recipient] += _amount;
    }

    function balanceOf(address _owner) public view returns (uint) {
        return balances[_owner];
    }
}

And this is how it looks like in Java

package com.u7.jthereum.exampleContracts;

import com.u7.jthereum.annotations.*;
import com.u7.jthereum.internal.*;
import com.u7.jthereum.types.*;
import com.u7.jthereum.wellKnownInterfaces.*;

import static com.u7.util.gg.cf;
import static com.u7.jthereum.Jthereum.*;
import static com.u7.jthereum.SolidityStaticImports.*;

public class BasicToken implements ERC20<BasicToken>
{
	public final String name = "Basic Token";
	public final String symbol = "BAS";

	public final Uint8 decimals = Uint8.valueOf(8);

	private final Uint256 initialSupply = Uint256.valueOf(100_000_000_000_000_000L);

	// All of the balances
	final Mapping<Address, Uint256> balancesByAddress = new Mapping<>();

	public BasicToken()
	{
		// set up initial supply
		balancesByAddress.put(msg.sender, initialSupply);
	}

	@Override
	public boolean transfer(final Address _recipient, final Uint256 _amount)
	{
		require(balancesByAddress.get(msg.sender).greaterThanOrEqual(_amount), "Not enough funds");
		require(!_recipient.equals(msg.sender), "No need to send tokens to yourself");

		// Compute the new balances
		final Uint256 newSenderBalance = balancesByAddress.get(msg.sender).subtract(_amount);
		final Uint256 newRecipientBalance = balancesByAddress.get(_recipient).add(_amount);

		require(newRecipientBalance.greaterThanOrEqual(balancesByAddress.get(_recipient))); //overflow check

		balancesByAddress.put(msg.sender, newSenderBalance);
		balancesByAddress.put(_recipient, newRecipientBalance);

		// Log the transaction
		emitEvent(new Transfer(msg.sender, _recipient, _amount));

		return true;
	}

	@Override
	@View
	public Uint256 balanceOf(final Address who)
	{
		return balancesByAddress.get(who);
	}

	public static void main(final String[] args)
	{
		compileAndDeploy();

		final BasicToken t = (BasicToken)createProxy();

		// burn some tokens
		t.transfer(Address.ZERO, new Uint256(1000));

		String myAddress = getMyAddress();
		p("My Balance: " + cf(t.balanceOf(new Address(myAddress))));
	}
}

What happens when we build and run the code? Well, Jthereum converts your Java code into the Solidity code. Take a look at it:

Compiling BasicToken
Compiling com.u7.jthereum.wellKnownInterfaces.ERC20

Solidity Source:

// Generated by Jthereum BETA version!
pragma solidity ^0.5.9;
contract BasicToken
{
	string public name = "Basic Token";
	string public symbol = "BAS";
	uint8 public decimals = 8;
	uint256 private initialSupply = 100_000_000_000_000_000;
	mapping (address => uint256) private balancesByAddress;
	constructor() public 
	{
		balancesByAddress[msg.sender] = initialSupply;
	}
	function transfer(address _recipient, uint256 _amount) public returns (bool) 
	{
		require((balancesByAddress[msg.sender] >= _amount), "Not enough funds");
		require(!(_recipient == msg.sender), "No need to send tokens to yourself");
		uint256 newSenderBalance = (balancesByAddress[msg.sender] - _amount);
		uint256 newRecipientBalance = (balancesByAddress[_recipient] + _amount);
		require((newRecipientBalance >= balancesByAddress[_recipient]));
		balancesByAddress[msg.sender] = newSenderBalance;
		balancesByAddress[_recipient] = newRecipientBalance;
		emit Transfer(msg.sender, _recipient, _amount);
		return true;
	}
	function balanceOf(address who) public view returns (uint256) 
	{
		return balancesByAddress[who];
	}


	// Imported Event declarations
	event Transfer(address indexed from, address indexed to, uint256 value);

	event Approval(address indexed owner, address indexed spender, uint256 value);


}

Then your Solidity code is being compiled and deployed on the Blockchain. In this case we specified the blockchain to be “ropsten”. Take a look at the output:

Argument values for call to Jthereum.compileAndDeploy(): 

	 Argument 										    Source 
	==========										   ========
	String blockchainName = "ropsten";							// directly supplied
	String web3jURL = "http://ropsten.jthereum.com:8545";					// global property: ROPSTEN_Web3j_URL
	Class contractClass = BasicToken.class;							// call stack (when called from ‘main()’ method on class to be deployed)
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// global property: ROPSTEN_PrivateKey
	BigInteger gasPrice = 15,000,000,000;							// default gas price for 'ropsten' blockchain
	BigInteger gasLimit = 4,000,000;							// default gas limit for 'ropsten' blockchain


Deploying contract to the blockchain

Tx hash: 0xfe52b5307420cf75c5c48b644eaea3474e5f98075377b0398052d5b5695891a9
Waiting for transaction to be mined.
Your contract was deployed in block #5,999,310
The new contract address is at: 0xf4c6a308757eb2e4cbfe137011c09dd2c7cbed39

Preparing to validate contract source code on Etherscan for blockchain 'ropsten'
Validating contract source code on Etherscan for blockchain 'ropsten'
Version hash: 5a6ea5b1
Compiler Version: v0.5.10+commit.5a6ea5b1
Result: {"status":"1","message":"OK","result":"ebfrwmpbjakx1u1u7i9gvru3tstf5zs3zzgzmiqrdm3usdw3vp"}

Contract source code validation has been submitted.  You can view your contract on Etherscan at: 
https://ropsten.etherscan.io/address/0xf4c6a308757eb2e4cbfe137011c09dd2c7cbed39

Now argument values for Jthereum Proxy:

Argument values for call to Jthereum.createProxy(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicToken.class;							// call stack (when called from ‘main()’ method on class to be deployed)
	String blockchainName = "ropsten";							// most recent deployment for class BasicToken
	String web3jURL = "http://ropsten.jthereum.com:8545";					// global property: ROPSTEN_Web3j_URL
	String address = "0xf4c6a308757eb2e4cbfe137011c09dd2c7cbed39";				// most recent deployment to the blockchain 'ropsten' for class BasicToken
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// global property: ROPSTEN_PrivateKey

Finally, here is our output result:

Argument values for call to ContractProxyContextInfo.callContractTransaction(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicToken.class;							// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xf4c6a308757eb2e4cbfe137011c09dd2c7cbed39";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration
	BigInteger gasPrice = 15,000,000,000;							// default gas price for 'ropsten' blockchain
	BigInteger gasLimit = 4,000,000;							// default gas limit for 'ropsten' blockchain


Calling transfer:

Tx hash: 0x8412a91b1f22f9a89391e84045f2aec5517b1a08b38a8fa705a0063add7f7b33
Waiting for transaction to be mined.
Gas Used: 49,936
Total WEI used: 749,040,000,000,000
Total ETH used: 0.000749
(Gas Price: 15,000,000,000 wei)
Transaction succeeded with status: 0x1


Argument values for call to Jthereum.getMyAddress(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicToken.class;							// call stack (when called from ‘main()’ method on class to be deployed)
	String blockchainName = "ropsten";							// most recent deployment for class BasicToken
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// global property: ROPSTEN_PrivateKey



Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicToken.class;							// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xf4c6a308757eb2e4cbfe137011c09dd2c7cbed39";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration


Calling balanceOf:
My Balance: 99,999,999,999,999,000

Basic Info Getter Contract

On the Ethereum blockchain you can interact with different contracts. It creates a huge opportunity for various use cases. In this example we use different methods to retrieve information of a contract.

• It returns an address of the contract
• It returns an address of the contract’s owner
• It returns an address of the sender
• It returns a balance of the contract
• It returns a balance of the contract’s owner (ONLY if you are the owner)
• It returns a balance of the sender

If you wanted to write this contract in Solidity it would look as following:

pragma solidity ^0.4.22;

contract Checker {
    address owner;
    
    constructor() public {
        owner = msg.sender;    
    }
    
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }
    
    function getBalanceOfContract() public view returns(uint) {
        return address(this).balance;
    }
    
    function getBalanceOfOwner() public view onlyOwner returns(uint){
        return owner.balance;
    }
    
    function getBalanceOfSender() public view returns(uint) {
        return msg.sender.balance;
    }
    
    function getAddressOfContract() public view returns(address) {
        return this;
    }
   
    function getAddressOfOwner() public view returns(address) {
        return owner;    
    }
     
    function getAddressOfSender() public view returns(address) {
        return msg.sender;
    }
}

And this is how it looks like in Java

package com.u7.jthereum.exampleContracts;

import com.u7.jthereum.annotations.*;
import com.u7.jthereum.types.*;

import java.math.*;

import static com.u7.util.gg.cf;
import static com.u7.jthereum.Jthereum.*;
import static com.u7.jthereum.SolidityStaticImports.*;

public class BasicInfoGetter
{
	Address owner;

	public BasicInfoGetter()
	{
		owner = msg.sender;
	}

	// Allow the contract to receive payments
	@FallbackFunction
	@Payable
	public void fallbackFunction()
	{
	}

	@View
	public Uint getBalanceOfContract()
	{
		return address(this).balance;
	}

	@View
	public Uint getBalanceOfOwner()
	{
		onlyOwner();

		return owner.balance;
	}

	@View
	public Uint getBalanceOfSender()
	{
		return msg.sender.balance;
	}

	@View
	public Address getAddressOfContract()
	{
		return new Address(this);
	}

	@View
	public Address getAddressOfOwner()
	{
		return owner;
	}

	@View
	public Address getAddressOfSender()
	{
		return msg.sender;
	}

	@View
	private void onlyOwner()
	{
		require(isOwner(), "Only owner can do that!");
	}

	@View
	private boolean isOwner()
	{
		return msg.sender.equals(owner);
	}



	public static void main(final String[] args)
	{
		final String address = compileAndDeploy("ropsten");

		// Send a few Wei to the contract
		sendEth(address, BigInteger.valueOf(5));

		final BasicInfoGetter a = createProxy(BasicInfoGetter.class);

		p("Address of Contract: " + a.getAddressOfContract());
		p("Address of Owner: " + a.getAddressOfOwner());
		p("Address of Sender: " + a.getAddressOfSender());
		p("Balance of Contract: " + cf(a.getBalanceOfContract()));
		p("Balance of Owner: " + cf(a.getBalanceOfOwner()));
		p("Balance of Sender: " + cf(a.getBalanceOfSender()));
	}
}

What happens when we build and run the code? Well, Jthereum converts your Java code into the Solidity code. Take a look at it:

Compiling BasicInfoGetter

Solidity Source:

// Generated by Jthereum BETA version!
pragma solidity ^0.5.9;
contract BasicInfoGetter
{
	address private owner;
	constructor() public 
	{
		owner = msg.sender;
	}
	function () external payable 
	{
	}
	function getBalanceOfContract() public view returns (uint) 
	{
		return address(this).balance;
	}
	function getBalanceOfOwner() public view returns (uint) 
	{
		onlyOwner();
		return owner.balance;
	}
	function getBalanceOfSender() public view returns (uint) 
	{
		return msg.sender.balance;
	}
	function getAddressOfContract() public view returns (address) 
	{
		return address(this);
	}
	function getAddressOfOwner() public view returns (address) 
	{
		return owner;
	}
	function getAddressOfSender() public view returns (address) 
	{
		return msg.sender;
	}
	function onlyOwner() private view 
	{
		require(isOwner(), "Only owner can do that!");
	}
	function isOwner() private view returns (bool) 
	{
		return (msg.sender == owner);
	}

}

Then your Solidity code is being compiled and deployed on the Blockchain. In this case we specified the blockchain to be “ropsten”. Take a look at the output:

Argument values for call to Jthereum.compileAndDeploy(): 

	 Argument 										    Source 
	==========										   ========
	String blockchainName = "ropsten";							// directly supplied
	String web3jURL = "http://ropsten.jthereum.com:8545";					// global property: ROPSTEN_Web3j_URL
	Class contractClass = BasicInfoGetter.class;						// call stack (when called from ‘main()’ method on class to be deployed)
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// global property: ROPSTEN_PrivateKey
	BigInteger gasPrice = 15,000,000,000;							// default gas price for 'ropsten' blockchain
	BigInteger gasLimit = 4,000,000;							// default gas limit for 'ropsten' blockchain


Deploying contract to the blockchain

Tx hash: 0x51a2f9ec5b1f13c31db7d4390972d827569b990e050af8820efbf9998f401780
Waiting for transaction to be mined.
Your contract was deployed in block #5,999,333
The new contract address is at: 0xfd324349df87ffa88f245b90e67f3ed6928358e3

Preparing to validate contract source code on Etherscan for blockchain 'ropsten'
Validating contract source code on Etherscan for blockchain 'ropsten'
Version hash: 5a6ea5b1
Compiler Version: v0.5.10+commit.5a6ea5b1
Result: {"status":"1","message":"OK","result":"uvx5ynhdqvu9vahhy1e2zpti3zp1bewq9f6wvusuhjuknuqsck"}

Contract source code validation has been submitted.  You can view your contract on Etherscan at: 
https://ropsten.etherscan.io/address/0xfd324349df87ffa88f245b90e67f3ed6928358e3

Argument values for call to Jthereum.sendEth(): 

	 Argument 										    Source 
	==========										   ========
	String address = "0xfd324349df87ffa88f245b90e67f3ed6928358e3";				// directly supplied
	Class contractClass = BasicInfoGetter.class;						// call stack (when called from ‘main()’ method on class to be deployed)
	String blockchainName = "ropsten";							// most recent deployment for class BasicInfoGetter
	String web3jURL = "http://ropsten.jthereum.com:8545";					// global property: ROPSTEN_Web3j_URL
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// global property: ROPSTEN_PrivateKey
	BigInteger gasPrice = 15,000,000,000;							// default gas price for 'ropsten' blockchain
	BigInteger gasLimit = 4,000,000;							// default gas limit for 'ropsten' blockchain


Tx hash: 0x3f2f8eb0b166429a3327a57f5cd695c01d83fda63ca10074f0c9074fed37d066
Waiting for transaction to be mined.
Gas Used: 21,040
Total WEI used: 315,600,000,000,000
Total ETH used: 0.000316
(Gas Price: 15,000,000,000 wei)
Total WEI sent as payment: 5
Total ETH sent as payment: 0.000000
Transaction succeeded with status: 0x1

Now argument values for Jthereum Proxy:

Argument values for call to Jthereum.createProxy(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicInfoGetter.class;						// directly supplied
	String blockchainName = "ropsten";							// most recent deployment for class BasicInfoGetter
	String web3jURL = "http://ropsten.jthereum.com:8545";					// global property: ROPSTEN_Web3j_URL
	String address = "0xfd324349df87ffa88f245b90e67f3ed6928358e3";				// most recent deployment to the blockchain 'ropsten' for class BasicInfoGetter
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// global property: ROPSTEN_PrivateKey

Finally, here is our output result:

Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicInfoGetter.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xfd324349df87ffa88f245b90e67f3ed6928358e3";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration


Calling getAddressOfContract (Not a Transaction!):
Address of Contract: 0xfd324349df87ffa88f245b90e67f3ed6928358e3

Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicInfoGetter.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xfd324349df87ffa88f245b90e67f3ed6928358e3";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration


Calling getAddressOfOwner (Not a Transaction!):
Address of Owner: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa

Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicInfoGetter.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xfd324349df87ffa88f245b90e67f3ed6928358e3";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration


Calling getAddressOfSender (Not a Transaction!):
Address of Sender: 0x0000000000000000000000000000000000000000

Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicInfoGetter.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xfd324349df87ffa88f245b90e67f3ed6928358e3";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration


Calling getBalanceOfContract (Not a Transaction!):
Balance of Contract: 5

Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicInfoGetter.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xfd324349df87ffa88f245b90e67f3ed6928358e3";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration


Calling getBalanceOfOwner (Not a Transaction!):
Balance of Owner: 3,963,877,391,197,344,453,575,983,046,348,115,674,221,700,746,820,753,546,331,534,351,508,065,746,944

Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = BasicInfoGetter.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xfd324349df87ffa88f245b90e67f3ed6928358e3";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration


Calling getBalanceOfSender (Not a Transaction!):
Balance of Sender: 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,631,340,667,420,729,232,106,129,639,935

Process finished with exit code 0

Incrementer Contract

This example contract demonstrates a simple non-constant (transactional) function you can perform on the Ethereum blockchain.

If you wanted to write this contract in Solidity it would look as following:

contract Incrementer {

    address creator;
    uint iteration;

    function Incrementer() public 
    {
        creator = msg.sender; 
        iteration = 0;
    }

    function increment() 
    {
        iteration = iteration + 1;
    }
    
    function getIteration() constant returns (uint) 
    {
        return iteration;
    }
    
    /**********
     Standard kill() function to recover funds 
    **********/
    
    function kill() 
    { 
        if (msg.sender == creator)
            suicide(creator);  // kills this contract and sends remaining funds back to creator
    }
    
}

And this is how it looks like in Java

package com.u7.jthereum.exampleContracts;

import com.u7.jthereum.annotations.*;
import com.u7.jthereum.types.*;

import static com.u7.jthereum.Jthereum.*;
import static com.u7.jthereum.SolidityStaticImports.*;

public class Incrementer
{
	AddressPayable creator;
	Uint iteration;

	public Incrementer()
	{
		creator = msg.sender;
		iteration = Uint.ZERO;
	}

	public void increment()
	{
		iteration.increment();
	}

	@View
	@Constant
	public Uint getIteration()
	{
		return iteration;
	}

	/**********
	 Standard kill() function to recover funds
	 **********/

	public void kill()
	{
		if(msg.sender.equals(creator))
		{
			selfdestruct(creator);  // kills this contract and sends remaining funds back to creator
		}
	}

	public static void main(final String[] args)
	{
		compileAndDeploy();

		final Incrementer a = createProxy(Incrementer.class);

		a.increment();
		a.increment();

		p("Iteration: " + a.getIteration().asBigInteger());
	}
}

What happens when we build and run the code? Well, Jthereum converts your Java code into the Solidity code. Take a look at it:

Compiling Incrementer

Solidity Source:

// Generated by Jthereum BETA version!
pragma solidity ^0.5.9;
contract Incrementer
{
	address payable private creator;
	uint private iteration;
	constructor() public 
	{
		creator = msg.sender;
		iteration = 0;
	}
	function increment() public 
	{
		(iteration ++);
	}
	function getIteration() public view returns (uint) 
	{
		return iteration;
	}
	function kill() public 
	{
		if ((msg.sender == creator)) 
		{
			selfdestruct(creator);
		}
	}

}

Then your Solidity code is being compiled and deployed on the Blockchain. In this case we specified the blockchain to be “ropsten”. Take a look at the output:

Argument values for call to Jthereum.compileAndDeploy(): 

	 Argument 										    Source 
	==========										   ========
	String blockchainName = "ropsten";							// directly supplied
	String web3jURL = "http://ropsten.jthereum.com:8545";					// global property: ROPSTEN_Web3j_URL
	Class contractClass = Incrementer.class;						// call stack (when called from ‘main()’ method on class to be deployed)
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// global property: ROPSTEN_PrivateKey
	BigInteger gasPrice = 15,000,000,000;							// default gas price for 'ropsten' blockchain
	BigInteger gasLimit = 4,000,000;							// default gas limit for 'ropsten' blockchain


Deploying contract to the blockchain

Tx hash: 0x6ba7dfe9f8361392aec11484faad17ab38c29eaf9d2c40cc9a24dae202a7bcfe
Waiting for transaction to be mined.
Your contract was deployed in block #5,999,354
The new contract address is at: 0xe1b34b1f593fba1a79d686f60e4d4b45b7402c95

Preparing to validate contract source code on Etherscan for blockchain 'ropsten'
Validating contract source code on Etherscan for blockchain 'ropsten'
Version hash: 5a6ea5b1
Compiler Version: v0.5.10+commit.5a6ea5b1
Result: {"status":"1","message":"OK","result":"uapsz3mfksjkjwfbtbctckgcgul7p88cnb598nivcmuyi9ynck"}

Contract source code validation has been submitted.  You can view your contract on Etherscan at: 
https://ropsten.etherscan.io/address/0xe1b34b1f593fba1a79d686f60e4d4b45b7402c95

Now argument values for Jthereum Proxy:

Argument values for call to Jthereum.createProxy(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = Incrementer.class;						// directly supplied
	String blockchainName = "ropsten";							// most recent deployment for class Incrementer
	String web3jURL = "http://ropsten.jthereum.com:8545";					// global property: ROPSTEN_Web3j_URL
	String address = "0xe1b34b1f593fba1a79d686f60e4d4b45b7402c95";				// most recent deployment to the blockchain 'ropsten' for class Incrementer
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// global property: ROPSTEN_PrivateKey

Finally, here is our output result:

Argument values for call to ContractProxyContextInfo.callContractTransaction(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = Incrementer.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xe1b34b1f593fba1a79d686f60e4d4b45b7402c95";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration
	BigInteger gasPrice = 15,000,000,000;							// default gas price for 'ropsten' blockchain
	BigInteger gasLimit = 4,000,000;							// default gas limit for 'ropsten' blockchain


Calling increment:

Tx hash: 0x0d0a3f33e4ce3e34fcc3c00d5fc8b39f285757134660d557f4a3c2c2649b88fb
Waiting for transaction to be mined.
Gas Used: 41,631
Total WEI used: 624,465,000,000,000
Total ETH used: 0.000624
(Gas Price: 15,000,000,000 wei)
Transaction succeeded with status: 0x1


Argument values for call to ContractProxyContextInfo.callContractTransaction(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = Incrementer.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xe1b34b1f593fba1a79d686f60e4d4b45b7402c95";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration
	BigInteger gasPrice = 15,000,000,000;							// default gas price for 'ropsten' blockchain
	BigInteger gasLimit = 4,000,000;							// default gas limit for 'ropsten' blockchain


Calling increment:

Tx hash: 0xf303f3ab84f2c0d84a5d8a808a535faf3bc56c83032b6e922cd15785733b3c42
Waiting for transaction to be mined.
Gas Used: 26,631
Total WEI used: 399,465,000,000,000
Total ETH used: 0.000399
(Gas Price: 15,000,000,000 wei)
Transaction succeeded with status: 0x1


Argument values for call to ContractProxyContextInfo.callContractViewOrPure(): 

	 Argument 										    Source 
	==========										   ========
	Class contractClass = Incrementer.class;						// inherited from Proxy Object configuration
	String blockchainName = "ropsten";							// inherited from Proxy Object configuration
	String web3jURL = "http://ropsten.jthereum.com:8545";					// inherited from Proxy Object configuration
	String address = "0xe1b34b1f593fba1a79d686f60e4d4b45b7402c95";				// inherited from Proxy Object configuration
	BigInteger privateKey = pk for address: 0xb9e071fbc62fa28e9895b6031818ce20765fb6aa;	// inherited from Proxy Object configuration


Calling getIteration (Not a Transaction!):
Iteration: 2

Process finished with exit code 0