java中任何只设置被选中字体，我用是是JTextPanel做文本域，谢谢大家来解答！

自己改改看吧
import java.awt.EventQueue;

import javax.swing.*;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
import javax.swing.text.*;

public class T {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
JFrame frm = new JFrame();
final DefaultStyledDocument model = new DefaultStyledDocument();
final JTextPane p = new JTextPane(model);
p.addCaretListener(new CaretListener() {
int start = 0;
int length = 0;

@Override
public void caretUpdate(CaretEvent e) {
model.setCharacterAttributes(start, length,
new SimpleAttributeSet() {