A DESCRIPTION OF THE PROBLEM :
The HTMLDocument.getIterator(HTML.Tag) method contains incomplete implementation for block-level elements. When called with any block-level tag (where tag.isBlock() returns true), the method immediately returns null due to a "TBD" (To Be Done) comment in the source code, rather than providing the expected iterator functionality.

    public Iterator getIterator(HTML.Tag t) {
        if (t.isBlock()) {
            // TBD
            return null;
        }
        return new LeafIterator(t, this);
    }


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import javax.swing.JTextPane;
import javax.swing.text.html.HTML;
import javax.swing.text.html.HTMLDocument;

public class IteratorTest {
    private static JTextPane editor;

    public static void main(String[] args) {
        editor = new JTextPane();
        editor.setContentType("text/html");
        HTMLDocument doc = (HTMLDocument) editor.getDocument();
        HTMLDocument.Iterator bodyIt = doc.getIterator(HTML.Tag.BODY);
        if (bodyIt == null) {
            throw new RuntimeException("Test Failed: Iterator for BODY tag is null");
        }
    }
}

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