fix static initialization in AbstractDatastoreFactory

Author: diegomarquezp

google-http-client/src/main/java/com/google/api/client/util/store/AbstractDataStoreFactory.java

@@ -41,7 +41,11 @@ public abstract class AbstractDataStoreFactory implements DataStoreFactory {
  * Pattern to control possible values for the {@code id} parameter of {@link
  * #getDataStore(String)}.
  */
- private static final Pattern ID_PATTERN = Pattern.compile("\\w{1,30}");
+ private static final Pattern ID_PATTERN;
+
+ static {
+ ID_PATTERN = Pattern.compile("\\w{1,30}");
+ }
 
  public final <V extends Serializable> DataStore<V> getDataStore(String id) throws IOException {
  Preconditions.checkArgument(