Swing

import javax.swing.JButton;
import javax.swing.JEditorPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.UIManager;
import javax.swing.WindowConstants;
import javax.swing.text.AttributeSet;
import javax.swing.text.DefaultStyledDocument;
import javax.swing.text.Document;
import javax.swing.text.EditorKit;
import javax.swing.text.MutableAttributeSet;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyledDocument;
import javax.swing.text.StyledEditorKit;

public class NewJFrame extends javax.swing.JFrame implements ActionListener {
 private JPanel jp1;

 private JButton color;

 private JTextPane jep;

 private JScrollPane jsp;

 private JButton font;

 /**
  * Auto-generated main method to display this JFrame
  */
 public static void main(String[] args) {
  NewJFrame inst = new NewJFrame();
  inst.setVisible(true);
 }

 public NewJFrame() {
  super();
  initGUI();
 }

 private void initGUI() {
  try {
   BorderLayout thisLayout = new BorderLayout();
   getContentPane().setLayout(thisLayout);
   setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
   {
    jp1 = new JPanel();
    getContentPane().add(jp1, BorderLayout.NORTH);
    {
     font = new JButton();
     font.addActionListener(this);
     jp1.add(font);
     font.setText("font");
    }
    {
     color = new JButton();
     jp1.add(color);
     color.addActionListener(this);
     color.setText("color");
    }
   }
   {
    jsp = new JScrollPane();
    getContentPane().add(jsp, BorderLayout.CENTER);
    {
     jep = new JTextPane();
     jsp.setViewportView(jep);
     jep.setDocument(new DefaultStyledDocument());
    }
   }
   pack();
   setSize(400, 300);
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public static void setFontSize(JEditorPane editor, int size) {
  if (editor != null) {
   if ((size > 0) && (size < 512)) {
    MutableAttributeSet attr = new SimpleAttributeSet();
    StyleConstants.setFontSize(attr, size);
    setCharacterAttributes(editor, attr, false);
   } else {
    UIManager.getLookAndFeel().provideErrorFeedback(editor);
   }
  }
 }

 public static void setForeground(JEditorPane editor, Color fg) {
  if (editor != null) {
   if (fg != null) {
    MutableAttributeSet attr = new SimpleAttributeSet();
    StyleConstants.setForeground(attr, fg);
    setCharacterAttributes(editor, attr, false);
   } else {
    UIManager.getLookAndFeel().provideErrorFeedback(editor);
   }
  }
 }

 public static final void setCharacterAttributes(JEditorPane editor,
   AttributeSet attr, boolean replace) {
  int p0 = editor.getSelectionStart();
  int p1 = editor.getSelectionEnd();
  if (p0 != p1) {
   StyledDocument doc = getStyledDocument(editor);
   doc.setCharacterAttributes(p0, p1 - p0, attr, replace);
  }
  StyledEditorKit k = getStyledEditorKit(editor);
  MutableAttributeSet inputAttributes = k.getInputAttributes();
  if (replace) {
   inputAttributes.removeAttributes(inputAttributes);
  }
  inputAttributes.addAttributes(attr);
 }

 protected static final StyledDocument getStyledDocument(JEditorPane e) {
  Document d = e.getDocument();
  if (d instanceof StyledDocument) {
   return (StyledDocument) d;
  }
  throw new IllegalArgumentException("document must be StyledDocument");
 }

 protected static final StyledEditorKit getStyledEditorKit(JEditorPane e) {
  EditorKit k = e.getEditorKit();
  if (k instanceof StyledEditorKit) {
   return (StyledEditorKit) k;
  }
  throw new IllegalArgumentException("EditorKit must be StyledEditorKit");
 }

 public void actionPerformed(ActionEvent e) {
  Object obj = e.getSource();
  if (obj == font) {
   JEditorPane editor = jep;
   setFontSize(editor, 20);
  }
  if (obj == color) {
   JEditorPane editor = jep;
   setForeground(editor, Color.red);
  }
 }

}
其他操作如下：
1、对字体的操作
MutableAttributeSet attr = new SimpleAttributeSet();
    StyleConstants.setFontFamily(attr, family);
    setCharacterAttributes(editor, attr, false);
family为字体
2、对字体大小的操作
MutableAttributeSet attr = new SimpleAttributeSet();
    StyleConstants.setFontSize(attr, size);
    setCharacterAttributes(editor, attr, false);
size为字号
3、是否是粗体的操作
StyledEditorKit kit = getStyledEditorKit(editor);
   MutableAttributeSet attr = kit.getInputAttributes();
   boolean bold = (StyleConstants.isBold(attr)) ? false : true;
   SimpleAttributeSet sas = new SimpleAttributeSet();
   StyleConstants.setBold(sas, bold);
   setCharacterAttributes(editor, sas, false);
4、是否是斜体的操作
StyledEditorKit kit = getStyledEditorKit(editor);
   MutableAttributeSet attr = kit.getInputAttributes();
   boolean italic = (StyleConstants.isItalic(attr)) ? false : true;
   SimpleAttributeSet sas = new SimpleAttributeSet();
   StyleConstants.setItalic(sas, italic);
   setCharacterAttributes(editor, sas, false);
5、是否有下划线的操作
StyledEditorKit kit = getStyledEditorKit(editor);
   MutableAttributeSet attr = kit.getInputAttributes();
   boolean underline = (StyleConstants.isUnderline(attr)) ? false
     : true;
   SimpleAttributeSet sas = new SimpleAttributeSet();
   StyleConstants.setUnderline(sas, underline);
   setCharacterAttributes(editor, sas, false);
6、左中右对齐的处理
MutableAttributeSet attr = new SimpleAttributeSet();
   StyleConstants.setAlignment(attr, a);
   setParagraphAttributes(editor, attr, false);
public static final void setParagraphAttributes(JEditorPane editor,
   AttributeSet attr, boolean replace) {
  int p0 = editor.getSelectionStart();
  int p1 = editor.getSelectionEnd();
  StyledDocument doc = getStyledDocument(editor);
  doc.setParagraphAttributes(p0, p1 - p0, attr, replace);
 }
a:0：左，1：中，2：右