Java Swing - 如何在JEditorPane中设置选定文本的字体大小使用JComboBox

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.Action;
import javax.swing.JComboBox;
import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultStyledDocument;
import javax.swing.text.Document;
import javax.swing.text.StyledDocument;
import javax.swing.text.StyledEditorKit;

public class Main extends JPanel {
  Integer[] ITEMS = { 9, 10, 11, 12, 14, 16, 18, 20, 24, 32 };
  JEditorPane editorPane = new JEditorPane();
  JComboBox<Integer> fontBox = new JComboBox<Integer>(ITEMS);
  StyledDocument doc = new DefaultStyledDocument();
  StyledEditorKit styledEditorKit = new StyledEditorKit();

  public Main() {
    editorPane.setDocument(doc);
    editorPane.setEditorKit(styledEditorKit);
    JScrollPane scrollpane = new JScrollPane(editorPane);
    scrollpane.setPreferredSize(new Dimension(500, 400));
    JPanel comboPanel = new JPanel();
    comboPanel.add(fontBox);

    setLayout(new BorderLayout());
    add(scrollpane, BorderLayout.CENTER);
    add(comboPanel, BorderLayout.SOUTH);

    Document doc = editorPane.getDocument();
    for (int i = 0; i < 20; i++) {
      int offset = doc.getLength();
      String str = "This is line number: " + i + "\n";
      try {
        doc.insertString(offset, str, null);
      } catch (BadLocationException e) {
        e.printStackTrace();
      }
    }

    fontBox.addActionListener(e -> {
      int size = (Integer) fontBox.getSelectedItem();
      Action fontAction = new StyledEditorKit.FontSizeAction(String
          .valueOf(size), size);
      fontAction.actionPerformed(e);
    });
  }

  public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(new Main());
    frame.pack();
     frame.setVisible(true);
  }
}