Add CheckStellarAssetContract example

examples/src/main/java/network/lightsail/CheckStellarAssetContract.java

@@ -0,0 +1,57 @@
+package network.lightsail;
+
+import java.io.IOException;
+import java.util.List;
+import org.stellar.sdk.*;
+import org.stellar.sdk.responses.sorobanrpc.GetLedgerEntriesResponse;
+import org.stellar.sdk.scval.Scv;
+import org.stellar.sdk.xdr.ContractDataDurability;
+import org.stellar.sdk.xdr.LedgerEntry.LedgerEntryData;
+import org.stellar.sdk.xdr.LedgerEntryType;
+import org.stellar.sdk.xdr.LedgerKey;
+import org.stellar.sdk.xdr.LedgerKey.LedgerKeyContractData;
+
+/**
+ * This example shows how to check the existence of the SAC (Stellar Asset Contract) of a class
+ * asset.
+ */
+public class CheckStellarAssetContract {
+  public static void main(String[] args) throws IOException {
+    String rpcServerUrl = "https://soroban-testnet.stellar.org:443";
+    Network network = Network.TESTNET;
+    Asset assetNative = Asset.createNativeAsset();
+    Asset assetUSDC =
+        Asset.createNonNativeAsset(
+            "USDC", "GDQOE23CFSUMSVQK4Y5JHPPYK73VYCNHZHA7ENKCV37P6SUEO6XQBKPP");
+    Asset assetUnknown =
+        Asset.createNonNativeAsset(
+            "UNKN", "GDQOE23CFSUMSVQK4Y5JHPPYK73VYCNHZHA7ENKCV37P6SUEO6XQBKPP");
+
+    try (SorobanServer sorobanServer = new SorobanServer(rpcServerUrl)) {
+      for (Asset asset : List.of(assetNative, assetUSDC, assetUnknown)) {
+        String contractId = asset.getContractId(network);
+        System.out.printf(
+            "The contract id for %s is %s, it is %s\n",
+            asset,
+            contractId,
+            isContractDeployed(sorobanServer, contractId) ? "deployed" : "not deployed");
+      }
+    }
+  }
+
+  public static boolean isContractDeployed(SorobanServer sorobanServer, String contractId) {
+    List<LedgerKey> ledgerKeys =
+        List.of(
+            LedgerKey.builder()
+                .discriminant(LedgerEntryType.CONTRACT_DATA)
+                .contractData(
+                    LedgerKeyContractData.builder()
+                        .contract(new Address(contractId).toSCAddress())
+                        .key(Scv.toLedgerKeyContractInstance())
+                        .durability(ContractDataDurability.PERSISTENT)
+                        .build())
+                .build());
+    GetLedgerEntriesResponse response = sorobanServer.getLedgerEntries(ledgerKeys);
+    return response.getEntries() != null && !response.getEntries().isEmpty();
+  }
+}