title: 'optional repeated' with google protobuf for Java
body: <p>I am using Google Protobuf using java.
  I wrote a statement like </p>
  
  <pre><code>optional repeated   string  users = 9;
  </code></pre>
  
  <p>When I tried to compile I am getting an error like </p>
  
  <pre><code>message.proto:39:57: Missing field number.
  </code></pre>
  
  <p>All I wanted was to create an array of strings.</p>
  
  <p>Can anybody help me to resolve it.</p>
  
  <p>PS: If I avoided optional keyword then it is compiling but in java I am getting a class not found error for <code>com.google.protobuf.ProtocolStringList</code></p>
  
  <p>Thanks in advance</p>