title: Open api 3.0 java code generator - How to generate instantiated lists?
body: <p>A few weeks ago, we migrate our project Swagger 2.0 files to Open api 3.0. We use the Java code generator to generate our classes. </p>
  
  <p>With the Swagger 2.0 and the swagger-codegen-cli-2.2.2.jar, the lists where generated like that:</p>
  
  <pre><code>private List&lt;Betriebspunkt&gt; ist = new ArrayList&lt;Betriebspunkt&gt;();
  private List&lt;Betriebspunkt&gt; plan = new ArrayList&lt;Betriebspunkt&gt;();
  </code></pre>
  
  <p>Now, with Open api 3.0 and openapi-generator-cli-3.3.2-20181022.194157-15.jar, my object is generated like that:</p>
  
  <pre><code>private List&lt;Betriebspunkt&gt; ist = null;
  private List&lt;Betriebspunkt&gt; plan = null;
  </code></pre>
  
  <p>My yaml file looks like that:</p>
  
  <pre><code>Zuglauf:
    properties:
      ist:
        type: array
        items:
          $ref: '#/components/schemas/Betriebspunkt'
      plan:
        type: array
        items:
          $ref: '#/components/schemas/Betriebspunkt'
    type: object
  </code></pre>
  
  <p>I don't want my lists declared as null. I looked in the generator java options (<a href="https://github.com/OpenAPITools/openapi-generator/blob/master/docs/generators/java.md" rel="nofollow noreferrer">https://github.com/OpenAPITools/openapi-generator/blob/master/docs/generators/java.md</a>), but I didn't find any solution. Is there any way to get my lists instantiated?</p>