Add Java SDK Example.

docs/soroban-internals/contract-interactions/stellar-transaction.mdx

@@ -255,6 +255,126 @@ else:
     print(f"Transaction failed: {get_response.result_xdr}")
 ```
 
+</TabItem>
+<TabItem value="java" label="Java">
+
+:::tip
+
+[java-stellar-sdk](https://github.com/stellar/java-stellar-sdk) provides support for Soroban, please visit the project homepage for more information.
+
+:::
+
+```java
+import java.io.IOException;
+import org.stellar.sdk.AccountNotFoundException;
+import org.stellar.sdk.InvokeHostFunctionOperation;
+import org.stellar.sdk.KeyPair;
+import org.stellar.sdk.Network;
+import org.stellar.sdk.PrepareTransactionException;
+import org.stellar.sdk.SorobanServer;
+import org.stellar.sdk.Transaction;
+import org.stellar.sdk.TransactionBuilder;
+import org.stellar.sdk.TransactionBuilderAccount;
+import org.stellar.sdk.requests.sorobanrpc.SorobanRpcErrorResponse;
+import org.stellar.sdk.responses.sorobanrpc.GetTransactionResponse;
+import org.stellar.sdk.responses.sorobanrpc.SendTransactionResponse;
+import org.stellar.sdk.scval.Scv;
+import org.stellar.sdk.xdr.TransactionMeta;
+
+public class SorobanExample {
+  public static void main(String[] args)
+      throws SorobanRpcErrorResponse, IOException, InterruptedException {
+
+    // The source account will be used to sign and send the transaction.
+    KeyPair sourceKeypair =
+        KeyPair.fromSecretSeed("SCQN3XGRO65BHNSWLSHYIR4B65AHLDUQ7YLHGIWQ4677AZFRS77TCZRB");
+
+    // Configure SorobanClient to use the `soroban-rpc` instance of your choosing.
+    SorobanServer sorobanServer = new SorobanServer("https://soroban-testnet.stellar.org");
+
+    // Here we will use a deployed instance of the `increment` example contract.
+    String contractAddress = "CBEOJUP5FU6KKOEZ7RMTSKZ7YLBS5D6LVATIGCESOGXSZEQ2UWQFKZW6";
+
+    // Transactions require a valid sequence number (which varies from one account to
+    // another). We fetch this sequence number from the RPC server.
+    TransactionBuilderAccount sourceAccount = null;
+    try {
+      sourceAccount = sorobanServer.getAccount(sourceKeypair.getAccountId());
+    } catch (AccountNotFoundException e) {
+      throw new RuntimeException("Account not found, please activate it first");
+    }
+
+    // The invocation of the `increment` function of our contract is added to the
+    // transaction. Note: `increment` doesn't require any parameters, but many
+    // contract functions do. You would need to provide those here.
+    InvokeHostFunctionOperation operation =
+        InvokeHostFunctionOperation.invokeContractFunctionOperationBuilder(
+                contractAddress, "increment", null)
+            .build();
+
+    // Create a transaction with the source account and the operation we want to invoke.
+    Transaction transaction =
+        new TransactionBuilder(sourceAccount, Network.TESTNET)
+            .addOperation(operation)
+            .setTimeout(30) // This transaction will be valid for the next 30 seconds
+            .setBaseFee(100) // The base fee is 100 stroops (0.00001 XLM)
+            .build();
+
+    // We use the RPC server to "prepare" the transaction. This simulating the
+    // transaction, discovering the storage footprint, and updating the transaction
+    // to include that footprint. If you know the footprint ahead of time, you could
+    // manually use `addFootprint` and skip this step.
+    try {
+      transaction = sorobanServer.prepareTransaction(transaction);
+    } catch (PrepareTransactionException e) {
+      // You should handle the error here
+      throw new RuntimeException(e);
+    }
+
+    // Sign the transaction with the source account's keypair.
+    transaction.sign(sourceKeypair);
+
+    // Let's see the base64-encoded XDR of the transaction we just built.
+    System.out.println("Signed prepared transaction XDR: " + transaction.toEnvelopeXdrBase64());
+
+    // Submit the transaction to the Soroban-RPC server. The RPC server will then
+    // submit the transaction into the network for us. Then we will have to wait,
+    // polling `getTransaction` until the transaction completes.
+    SendTransactionResponse response = sorobanServer.sendTransaction(transaction);
+    if (!SendTransactionResponse.SendTransactionStatus.PENDING.equals(response.getStatus())) {
+      throw new RuntimeException("Sending transaction failed");
+    }
+
+    // Poll `getTransaction` until the status is not "NOT_FOUND"
+    GetTransactionResponse getTransactionResponse;
+    while (true) {
+      System.out.println("Waiting for transaction confirmation...");
+      // See if the transaction is complete
+      getTransactionResponse = sorobanServer.getTransaction(response.getHash());
+      if (!GetTransactionResponse.GetTransactionStatus.NOT_FOUND.equals(
+          getTransactionResponse.getStatus())) {
+        break;
+      }
+      // Wait one second
+      Thread.sleep(1000);
+    }
+
+    System.out.println("get_transaction response: " + getTransactionResponse);
+
+    if (GetTransactionResponse.GetTransactionStatus.SUCCESS.equals(
+        getTransactionResponse.getStatus())) {
+      // Find the return value from the contract and return it
+      TransactionMeta transactionMeta =
+          TransactionMeta.fromXdrBase64(getTransactionResponse.getResultMetaXdr());
+      long returnValue = Scv.fromUint32(transactionMeta.getV3().getSorobanMeta().getReturnValue());
+      System.out.println("Transaction result: " + returnValue);
+    } else {
+      System.out.println("Transaction failed: " + getTransactionResponse.getResultXdr());
+    }
+  }
+}
+```
+
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