title: JasperReport: Purpose of the Details Band
body: <p>I figured this would be something that would be fairly-well documented as its a central theme to JasperReports, however I can't find an answer for this anywhere.</p>
  
  <p><strong>What is the purpose/function/intention of a details band</strong>? Is it supposed to just be the central or core part of a report?</p>
  
  <p>From another question it was pointed out to me that there is a 1:1 relationship between a details band and a record/bean provided by the JRDatasource. This revelation brings to light a few tangential questions:</p>
  
  <ul>
  <li>It is possible to add detail bands programmatically in Java; what happens if you specify more/less detail bands (programmatically) than there are records/beans returned by your JRDataSource?</li>
  <li>What is the relationship between a details band, and say, a page inside an exported PDF document? Does 1 details bands translate to 1 page?</li>
  <li>What happens if you pass the <code>JasperFillManager</code> a <code>null</code> data source? Is it possible to still have detail bands?</li>
  </ul>
  
  <p>I don't like to ask multiple questions at a time, but these are so similarly-related I'd rather do it all at once than clutter SO with multiple nearly-identical questions. Thanks in advance.</p>