title: Why am I receiving a warning for missing type arguments and type conversion?
body: <p>My class is as following, and works fine, but NetBeans shows following warning on line 18, I am wondering what is that for?</p>
  
  <p><strong>Code</strong> </p>
  
  <pre><code>public class Users {
  
          private List&lt;Long&gt; grades;
  
          ...
          public String retrieveAllGrades(){
  
  Line 18    this.grades = new ArrayList();
  
             ...
          }
  
          getters and setters
  }
  </code></pre>
  
  <p><strong>Warning on line 18</strong> </p>
  
  <pre><code>Found raw type: ArrayList
  missing type arguments for generic class ArrayList&lt;E&gt; where E is a type-variable: E extends Object declared in class ArrayList
  
  [unchecked] unchecked conversion
  required: List&lt;Long&gt;
  found: ArrayList
  </code></pre>