title: The "Order and Export" tab in "Java Build Path"
body: <p><img src="https://i.stack.imgur.com/gFYoA.png" alt="enter image description here"></p>
  
  <p>What's the use of "Order and Export" tab in "Java Build Path" dialog box?
  By the name 'order', I can guess that JRE System library is searched before Plug-in Dependencies, but why do we have 'Export' in Build Path ? And what's it for the button left side of the elements? </p>
  
  <h2>ADDED</h2>
  
  <p>It's the example that I borrowed from <a href="https://rads.stackoverflow.com/amzn/click/com/0321288157" rel="noreferrer" rel="nofollow noreferrer">Eclipse distilled</a>.</p>
  
  <p>The orderes.webapp depends on orders, but it's likely to use the classes defined in ubl and catalog. </p>
  
  <p><img src="https://i.stack.imgur.com/6mhyX.png?width=100pt" alt="enter image description here"></p>
  
  <p>In such a case, orders can export catalog and ubl so that the packages that depends on it can use catalog and ubl. </p>
  
  <p><img src="https://i.stack.imgur.com/3i6lN.png" alt="enter image description here"></p>
  
  <p>And something more about "Order and Export".</p>
  
  <ol>
  <li>The check of the left side button modifies the <code>.classpath</code> file to add <code>exported=true</code> such as <code>&lt;classpathentry exported="true" kind="lib" path="lib/log4j-1.2.7.jar"/&gt;</code>. </li>
  <li>The src is always checked, and you can't uncheck it. </li>
  </ol>
  
  <h3>References</h3>
  
  <ul>
  <li><a href="https://stackoverflow.com/questions/13960556/interpreting-eclipse-classpath-file">Interpreting eclipse .classpath file. What does &#39;kind=&quot;con&quot;&#39; and &#39;exported=&quot;true&quot;&#39; mean?</a></li>
  <li><a href="http://www.informit.com/articles/article.aspx?p=367962" rel="noreferrer">Configuring an Eclipse Java Project</a></li>
  <li><a href="http://help.eclipse.org/juno/index.jsp?topic=/org.eclipse.jdt.doc.user/reference/ref-properties-build-path.htm" rel="noreferrer">Java Build Path</a></li>
  </ul>