openrtb-core/src/main/java/com/google/openrtb/json/OpenRtbJsonUtils.java
public static void writeStrings(String fieldName, List<String> data, JsonGenerator gen)
      throws IOException {
    if (!data.isEmpty()) {
      gen.writeArrayFieldStart(fieldName);
      for (String d : data) {
        gen.writeString(d);
      }
      gen.writeEndArray();
    }
  }
public static void writeStrings(String fieldName, List<String> data, JsonGenerator gen)
      throws IOException {
    if (!data.isEmpty()) {
      gen.writeArrayFieldStart(fieldName);
      for (String d : data) {
        gen.writeString(d);
      }
      gen.writeEndArray();
    }
  }
Writes a string array if not empty.