fix sample for batch write

Author: ShuranZhang

samples/snippets/src/main/java/com/example/spanner/ChangeStreamsTxnExclusionSample.java

@@ -118,14 +118,17 @@ static void batchWriteAtLeastOnceExcludedFromChangeStreams(DatabaseClient client
                     .build())),
             Options.excludeTxnFromChangeStreams());
     for (BatchWriteResponse response : responses) {
-      if (response.getStatus().getCode() != Code.OK_VALUE) {
+      if (response.getStatus().getCode() == Code.OK_VALUE) {
+        System.out.printf(
+            "Mutation group have been applied with commit timestamp %s",
+            response.getIndexesList(), response.getCommitTimestamp());
+      } else {
         System.out.printf(
             "Mutation group could not be applied with error code %s and "
-                + "error message %s",
+                + "error message %s", response.getIndexesList(),
             Code.forNumber(response.getStatus().getCode()), response.getStatus().getMessage());
       }
     }
-    System.out.println("New singer inserted.");
   }
 
   static void pdmlExcludedFromChangeStreams(DatabaseClient client) {

samples/snippets/src/test/java/com/example/spanner/ChangeStreamsTxnExclusionSampleIT.java

@@ -102,7 +102,7 @@ public void testSetExcludeTxnFromChangeStreamsSampleSample() throws Exception {
     assertThat(out).contains("New singer inserted.");
 
     out = runSample(() -> ChangeStreamsTxnExclusionSample.batchWriteAtLeastOnceExcludedFromChangeStreams(client));
-    assertThat(out).contains("New singer inserted.");
+    assertThat(out).contains("have been applied");
 
     out = runSample(() -> ChangeStreamsTxnExclusionSample.pdmlExcludedFromChangeStreams(client));
     assertThat(out).contains("Singers deleted.");