Import code from internal repository to git

java/com/google/domain/registry/tools/params/OptionalStringParameter.java

@@ -0,0 +1,19 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.domain.registry.tools.params;
+
+/** Optional wrapper for StringParameter. */
+public final class OptionalStringParameter
+    extends OptionalParameterConverterValidator<String, StringParameter> {}