title: Get all packages of project
body: <p>I have the name of the project, so i can get the project by</p>
  
  <pre><code>IProject project = ResourcesPlugin.getWorkspace().getRoot().getProject(proj.getName());
  IJavaProject jProj = (IJavaProject) project.getNature(JavaCore.NATURE_ID);
  </code></pre>
  
  <p>after I got the project i want to get the names of all the packages in the project.</p>
  
  <p>How can I do it?</p>