title: What does this Holder<> do in Java?
body: <p>Can someone please explain this code?</p>
  
  <pre><code>public void getSupplierByZipCode(
      @WebParam(name = "zip", targetNamespace = "http://www.webservicex.net/")
      String zip,
      @WebParam(name = "GetSupplierByZipCodeResult", targetNamespace =  "http://www.webservicex.net/", mode = WebParam.Mode.OUT)
      Holder&lt;Boolean&gt; getSupplierByZipCodeResult,
      @WebParam(name = "SupplierDataLists", targetNamespace = "http://www.webservicex.net/", mode = WebParam.Mode.OUT)
      Holder&lt;SupplierDataList&gt; supplierDataLists);
  </code></pre>
  
  <p>I've never seen <code>Holder</code> before in Java.  What are <code>Holder&lt;Boolean&gt;</code> and <code>Holder&lt;SupplierDataList&gt;</code> in the function?  Are they like outputs??  I need the supplier data list from this function.</p>