use java.nio for tests

Author: diegomarquezp

google-http-client-test/src/test/java/com/google/api/client/test/util/store/FileDataStoreFactoryTest.java

@@ -14,13 +14,13 @@
 
 package com.google.api.client.test.util.store;
 
+import static java.nio.file.Files.createTempDirectory;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
 import com.google.api.client.util.store.DataStore;
 import com.google.api.client.util.store.FileDataStoreFactory;
 import com.google.common.collect.ImmutableSet;
-import com.google.common.io.Files;
 import java.io.File;
 import java.io.IOException;
 import org.junit.Test;
@@ -34,7 +34,7 @@ public class FileDataStoreFactoryTest extends AbstractDataStoreFactoryTest {
 
   @Override
   protected FileDataStoreFactory newDataStoreFactory() throws IOException {
-    File dataDir = Files.createTempDir();
+    File dataDir = createTempDirectory("temp").toFile();
     dataDir.deleteOnExit();
     return new FileDataStoreFactory(dataDir);
   }