title: Exception while compiling: wrong version 50.0, should be 49.0
body: <p>I am working an application with JXL API and when i tried compiling using eclipse IDE, it's working fine and the same is not compiling when i am trying to compile in Command prompt and showing the below exception..</p>
  
  <pre><code>Extract.java:6: cannot access jxl.read.biff.BiffException bad class file: C:\Program Files\Java\jdk1.5.0_01\jre\lib\ext\jxl.jar(jxl/read/biff/BiffException.class)
  class file has wrong version 50.0, should be 49.0
  Please remove or make sure it appears in the correct subdirectory of the classpa
  th.
  import jxl.read.biff.BiffException;
                       ^
  1 error
  </code></pre>
  
  <p>EDIT:</p>
  
  <p>I am able to executing using JDK 1.6. Since JDK 1.6 must also be compatible with lower versions, why doesn't it support the class files which were compiled in JDK 1.5.</p>