Java SDK

The Java SDK (Japtos) allows you to connect, explore, and interact with the Aptos blockchain from Java applications. It provides comprehensive support for account management, transaction signing, multi-signature accounts, and hierarchical deterministic wallets.

Installation

Maven

Add the GitHub Packages repository and dependency to your pom.xml:

<repositories>
  <repository>
    <id>github</id>
    <url>https://maven.pkg.github.com/aptos-labs/japtos</url>
  </repository>
</repositories>

<dependencies>
  <dependency>
    <groupId>com.aptos-labs</groupId>
    <artifactId>japtos</artifactId>
    <version>1.1.0</version>
  </dependency>
</dependencies>

Manual Installation

If you prefer to build from source, you can clone the repository and install it locally:

git clone https://github.com/aptos-labs/japtos.git
cd japtos
mvn clean install

Key Features

Advanced Cryptography: Ed25519 and MultiEd25519 signature schemes
Hierarchical Deterministic Wallets: BIP39/BIP44 support with mnemonic phrases
Multi-Signature Accounts: Threshold-based multi-signature transactions
BCS Serialization: Binary Canonical Serialization for Aptos transactions
HTTP Client: Robust REST client for Aptos API interactions
Comprehensive Testing: Extensive test suite covering all functionality

Examples

Quickstart Get started with the Java SDK in minutes

Account Management Learn how to create and manage accounts, including multi-signature and HD wallets

Building Transactions Learn how to build, sign, and submit transactions

Examples Explore comprehensive examples in the SDK repository

Network Support

The SDK supports all Aptos networks:

import com.aptoslabs.japtos.api.AptosConfig;
import com.aptoslabs.japtos.client.AptosClient;

// Connect to different networks
AptosConfig config = AptosConfig.builder()
    .network(AptosConfig.Network.MAINNET)  // or TESTNET, DEVNET, LOCALNET
    .build();

AptosClient client = new AptosClient(config);

Transfer APT Example

Here’s a quick example of how to transfer APT tokens:

import com.aptoslabs.japtos.account.Ed25519Account;
import com.aptoslabs.japtos.client.AptosClient;
import com.aptoslabs.japtos.api.AptosConfig;
import com.aptoslabs.japtos.transaction.*;
import com.aptoslabs.japtos.types.*;

// Setup client
AptosConfig config = AptosConfig.builder()
    .network(AptosConfig.Network.DEVNET)
    .build();
AptosClient client = new AptosClient(config);

// Create accounts
Ed25519Account alice = Ed25519Account.generate();
Ed25519Account bob = Ed25519Account.generate();

// Fund accounts (devnet only)
client.fundAccount(alice.getAccountAddress(), 100_000_000);
client.fundAccount(bob.getAccountAddress(), 100_000_000);

// Build transfer transaction
ModuleId moduleId = new ModuleId(
    AccountAddress.fromHex("0x1"),
    new Identifier("coin")
);

TransactionPayload payload = new EntryFunctionPayload(
    moduleId,
    new Identifier("transfer"),
    Arrays.asList(new TypeTag.Struct(new StructTag(
        AccountAddress.fromHex("0x1"),
        new Identifier("aptos_coin"),
        new Identifier("AptosCoin"),
        Arrays.asList()
    ))),
    Arrays.asList(
        new TransactionArgument.AccountAddress(bob.getAccountAddress()),
        new TransactionArgument.U64(1_000_000L)  // 0.01 APT
    )
);

// Get account sequence number and chain ID
long sequenceNumber = client.getAccountSequenceNumber(alice.getAccountAddress());
int chainId = client.getChainId();

// Build and sign transaction
RawTransaction rawTx = new RawTransaction(
    alice.getAccountAddress(),
    sequenceNumber,
    payload,
    1000000L,  // maxGasAmount
    100L,      // gasUnitPrice
    System.currentTimeMillis() / 1000 + 3600,  // expiration
    chainId
);

SignedTransaction signedTx = new SignedTransaction(
    rawTx,
    alice.signTransactionWithAuthenticator(rawTx)
);

// Submit and wait for transaction
PendingTransaction pendingTx = client.submitTransaction(signedTx);
Transaction tx = client.waitForTransaction(pendingTx.getHash());

System.out.println("Transaction completed: " + tx.isSuccess());