address review feedback: replace int[] with AtomicInteger

Author: westarle

google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ComputeEngineCredentialsTest.java

@@ -67,6 +67,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Queue;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
@@ -421,14 +422,14 @@ void getRequestMetadata_shouldInvalidateAccessTokenWhenScoped_newAccessTokenFrom
 
   @Test
   void getRequestMetadata_multipleCalls_usesCachedToken() throws IOException {
-    final int[] requestCount = new int[1];
+    final AtomicInteger requestCount = new AtomicInteger(0);
     MockMetadataServerTransportFactory transportFactory = new MockMetadataServerTransportFactory();
     transportFactory.transport =
         new MockMetadataServerTransport(SCOPE_TO_ACCESS_TOKEN_MAP) {
           @Override
           public LowLevelHttpRequest buildRequest(String method, String url) throws IOException {
             if (url.startsWith(ComputeEngineCredentials.getTokenServerEncodedUrl())) {
-              requestCount[0]++;
+              requestCount.incrementAndGet();
             }
             return super.buildRequest(method, url);
           }
@@ -440,11 +441,11 @@ public LowLevelHttpRequest buildRequest(String method, String url) throws IOExce
 
     Map<String, List<String>> metadata = credentials.getRequestMetadata(CALL_URI);
     TestUtils.assertContainsBearerToken(metadata, ACCESS_TOKEN);
-    assertEquals(1, requestCount[0]);
+    assertEquals(1, requestCount.get());
 
     Map<String, List<String>> metadata2 = credentials.getRequestMetadata(CALL_URI);
     TestUtils.assertContainsBearerToken(metadata2, ACCESS_TOKEN);
-    assertEquals(1, requestCount[0]);
+    assertEquals(1, requestCount.get());
   }
 
   @Test