public Builder setInput(com.google.cloud.texttospeech.v1beta1.SynthesisInput value) {
      if (inputBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        input_ = value;
      } else {
        inputBuilder_.setMessage(value);
      }
      bitField0_ |= 0x00000002;
      onChanged();
      return this;
    }
<pre>
Required. The Synthesizer requires either plain text or SSML as input.
</pre>

<code>
.google.cloud.texttospeech.v1beta1.SynthesisInput input = 2 [(.google.api.field_behavior) = REQUIRED];
</code>
java-texttospeech/proto-google-cloud-texttospeech-v1beta1/src/main/java/com/google/cloud/texttospeech/v1beta1/SynthesizeLongAudioRequest.java