title: how to resolve org.eclipse.core.internal.resources.ResourceException
body: <p>I never encountered this exception before</p>
  
  <pre><code>org.eclipse.core.internal.resources.ResourceException: Resource '/External Plug-in Libraries' is not open.
  at org.eclipse.core.internal.resources.Project.checkAccessible(Project.java:137)
  at org.eclipse.core.internal.resources.Project.isNatureEnabled(Project.java:817)
  at newmodulewizrd.ui.Integrate.printProjectInfo(Integrate.java:130)
  at newmodulewizrd.ui.Integrate.getWorkSpace(Integrate.java:123)
  at newmodulewizrd.ui.Integrate.presentOptionsAndAddToMain(Integrate.java:117)
  at newmodulewizrd.ui.Integrate$2.actionPerformed(Integrate.java:84)
  at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
  at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
  at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
  at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
  </code></pre>
  
  <p>this is my code</p>
  
  <pre><code>try {
    if (project.isNatureEnabled("org.eclipse.jdt.core.javanature")) {
      IJavaProject javaProject = JavaCore.create(project);
        if(flag2==0) {
          printPackageInfos(javaProject);
          flag2=1;
        } else {
          IPackageFragmentRoot srcFolder = cm.createNewSourceFolder(project);
          newModule = srcFolder.createPackageFragment(textfield.getText(), true,null);
          printPackageInfos(javaProject);
          try {
            cm.refreshWorkspace();
          } catch (CoreException e) {
            e.printStackTrace();
          }
        }
     } else {
       System.out.println("something went wrong here");
     }
   } catch (CoreException e) {
     e.printStackTrace();
   }
  </code></pre>
  
  <p><em>I suspect it is trying to access my 'jre system library [jre6] folder {below my src folder}' inside my java project</em></p>
  
  <p><strong>Any idea on how to resolve it?</strong></p>