public java.lang.String getSourceLanguageCode() {
      java.lang.Object ref = sourceLanguageCode_;
      if (!(ref instanceof java.lang.String)) {
        com.google.protobuf.ByteString bs = (com.google.protobuf.ByteString) ref;
        java.lang.String s = bs.toStringUtf8();
        sourceLanguageCode_ = s;
        return s;
      } else {
        return (java.lang.String) ref;
      }
    }
<pre>
Required. The ISO-639 language code of the input document if known, for
example, "en-US" or "sr-Latn". Supported language codes are listed in
[Language Support](https://cloud.google.com/translate/docs/languages).
</pre>

<code>string source_language_code = 2 [(.google.api.field_behavior) = REQUIRED];</code>

@return The sourceLanguageCode.
java-translate/proto-google-cloud-translate-v3/src/main/java/com/google/cloud/translate/v3/BatchTranslateDocumentRequest.java