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    <p>You do not really need a generic tree data structure for this. Consider the following example:</p> <pre><code>private static final class Menu { private Menu parent; private List&lt;Menu&gt; children; private String moduleName; private String moduleControllerName; private String moduleActionName; private String alias; } </code></pre> <p>(getters/setters ommited for conciseness)</p> <p>The <code>parent</code> field helps you set the parent menu and can be null for the root menu.</p> <p>Add the Children menu to the <code>children</code> field.</p> <p>With this you will be able to capture the needs of your hierarchical menu I hope.</p> <p>Now to build the query supposing you have a result set <code>rs</code>:</p> <pre><code>Menu menu; while (rs.hasNext()) { if (rs.get("parent_id") == null) { // it s the root menu = new Menu(rs.get("id"), /* etc... */); } else { menu = findMenuById(menu, rs.get("parent_id")); menu.addChild(new Menu(rs.get("id"), /* etc... */)); } </code></pre> <p>as for find <code>findMenuById</code> it could be something like:</p> <pre><code>private Menu findMenuById(Menu menu, Long id) { if (menu.getId() == id) return menu; for (Menu childMenu : menu.getChildren()) { Menu found = findMenuById(childMenu, id); if (found != null) return found; } return null; } </code></pre> <h3>edit</h3> <p>Here is a custom working implementation I made. I inserted your menu in the database and use result set. I should be almost the same with the custom abstraction of yours. </p> <pre><code>Menu root = null; Map&lt;Integer, Menu&gt; menus = new HashMap&lt;Integer, Menu&gt;(); final Database databaseConnection = Database.createConnection("test", "root", ""); final ResultSet rs = databaseConnection.executeQuery("SELECT * FROM test.menus;"); while ( rs.next() ) { final Menu menu = new Menu(rs.getInt("id")) .setAlias(rs.getString("alias")) .setModuleName(rs.getString("module_name")); final Integer parentId = rs.getInt("parent_id"); if (root == null &amp;&amp; parentId == 0) { root = menu; } else { menus.get(parentId).addSubMenu(menu); } menus.put(menu.getId(), menu); } rootMenu = root; databaseConnection.closeConnection(); </code></pre> <p><code>Note 1</code>: I used an <code>HashMap</code> to store the menus that are not attached to the root yet.</p> <p><code>Note 2</code>: This implementation wont work if there are more than one root menu.</p>
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    1. POHow to populating Modified Preorder Tree Traversal data into Java tree object?
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    1. COThank you. But How the SQL Query structure for this problem? is it need a recursive function to retrieve all data from database? I don't know any clue about it. How to detect if a row is a parent? then?
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      1. USOka Prinarjaya
    2. COHmmm..i think i need the data querying strategy. Ahhh hard to say.. :(
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    3. COThank you ph. I will try ur solution. And tommorow i will comeback again. thx u very much
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