title: R: rJava error with xlsx (0.4.2) package
body: <p>I am trying to use the xlsx package to fill a spreadsheet with information from an external file. Up until now, I have used addDataFrame() to put information into the spreadsheet, and everything about it that I have tried has been successful (fonts, colors, borders, etc.)</p>
  
  <p>The issue now is that I need to have a column of hyperlinks, and to do that I need to get or create the specific cells (I'm not sure which, and both give the same error). The following code:</p>
  
  <pre><code>library(xlsx)
  wb = createWorkbook(type="xlsx")
  sheet = createSheet(wb, sheetName="InProduction")
  createCell(1, 2)
  </code></pre>
  
  <p>Produces the error:</p>
  
  <blockquote>
    <p>Error in .jcall(row[[ir]], "Lorg/apache/poi/ss/usermodel/Cell;",
    "createCell",  :    RcallMethod: cannot determine object class</p>
  </blockquote>
  
  <p>After doing some poking around, I found the method it is trying to call is <a href="http://poi.apache.org/apidocs/org/apache/poi/ss/usermodel/Row.html#getFirstCellNum%28%29" rel="nofollow">from this API</a> with the call:</p>
  
  <pre><code>minColIx &lt;- .jcall(row[[ir]], "T", "getFirstCellNum")
  </code></pre>
  
  <p>Which seems to me like it ought to work, but it clearly doesn't. Can anyone shed some light on this?</p>
  
  <p>Thanks in advance!</p>