title: Why Eclipse does not see .jar file of a library?
body: <p>I have a java project in which I have "Referenced Libraries". In the "Referenced Libraries" I have a .jar file of a library that I use (I use only one external library).</p>
  
  <p>When I try to "Run -> Run" the code I have a NullPointerException. From my previous experience I know that it it (very likely) because my code does not see the library. </p>
  
  <p>I just started to use Eclipse and it can be the I do not "connect" libraries in a correct way. Should I use some options or additional action to force Eclipse to see the .jar file of the library?</p>
  
  <p><strong>ADDED:</strong></p>
  
  <p>By the right click on the library I get a drop-down menu in which I see "Build Path". My be I need to do something there?</p>