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This page gets a Java application talking to Hedera testnet: SDK install, operator credentials, balance query, and an HBAR transfer.

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Prerequisites

  • JDK 11 or later
  • Maven 3.8+ or Gradle 8+
  • A Hedera testnet account with ECDSA keys from the developer portal

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Step 1: Add the SDK dependency

For Maven, add to pom.xml: 
<dependencies>
    <dependency>
        <groupId>com.hedera.hashgraph</groupId>
        <artifactId>sdk</artifactId>
        <version>2.72.0</version>
    </dependency>
    <dependency>
        <groupId>io.grpc</groupId>
        <artifactId>grpc-netty-shaded</artifactId>
        <version>1.73.0</version>
    </dependency>
</dependencies>
For Gradle, add to build.gradle: 
dependencies {
    implementation 'com.hedera.hashgraph:sdk:2.72.0'
    implementation 'io.grpc:grpc-netty-shaded:1.73.0'
}
grpc-netty-shaded is the network transport. Without it the SDK compiles, then throws at runtime when you actually try to talk to the network.

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Step 2: Credentials

Create a .env file in your project root (and add it to .gitignore): 
OPERATOR_ID=0.0.1234
OPERATOR_KEY=302d300706052b8104000a032200033456...
OPERATOR_ID is your Hedera account ID. OPERATOR_KEY is the DER-encoded ECDSA private key; use the HEX Encoded Private Key value from the developer portal.

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Step 3: Connect, query, transfer

Create src/main/java/HederaQuickstart.java: 
import com.hedera.hashgraph.sdk.*;
import io.github.cdimascio.dotenv.Dotenv;

public class HederaQuickstart {

    public static void main(String[] args) throws Exception {
        Dotenv env = Dotenv.load();
        AccountId operatorId = AccountId.fromString(env.get("OPERATOR_ID"));
        PrivateKey operatorKey = PrivateKey.fromString(env.get("OPERATOR_KEY"));

        // Connect to testnet using the operator account as the default payer.
        Client client = Client.forTestnet();
        client.setOperator(operatorId, operatorKey);

        // 1. Query the operator's balance.
        Hbar balance = new AccountBalanceQuery()
            .setAccountId(operatorId)
            .execute(client)
            .hbars;
        System.out.println("Operator balance: " + balance);

        // 2. Transfer 1 HBAR to account 0.0.3 (a test recipient).
        AccountId recipient = AccountId.fromString("0.0.3");
        TransactionResponse response = new TransferTransaction()
            .addHbarTransfer(operatorId, Hbar.from(-1))
            .addHbarTransfer(recipient, Hbar.from(1))
            .execute(client);

        TransactionReceipt receipt = response.getReceipt(client);
        System.out.println("Transfer status: " + receipt.status);
        System.out.println("Transaction ID: " + response.transactionId);

        client.close();
    }
}
Add a .env loader to your dependencies if you don’t have one. io.github.cdimascio:dotenv-java:3.0.0 is the common pick.

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Step 4: Run it

# Maven (package as a JAR with dependencies, then run it)
mvn package
java -cp target/your-artifact-with-dependencies.jar HederaQuickstart

# Gradle
./gradlew run
Expected output: 
Operator balance: 10000 ℏ
Transfer status: SUCCESS
Transaction ID: 0.0.1234@1700000000.123456789
Look up the transaction on HashScan: 
https://hashscan.io/testnet/transaction/<transactionId>

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What’s next

Create an Account

Generate a new account programmatically and fund it from your operator.

Create a Token

Mint a native HTS token with custom supply and decimals.

Submit to a Topic

Publish a message to HCS for verifiable, ordered audit logs.

SDK Reference

Full API reference on GitHub.
The four Hiero SDKs (JavaScript, Java, Go, Python) share the same API surface, so code translates almost line-for-line between them. Differences are mostly language-idiomatic.