你可以使用这个技巧：

import java.awt.*;

public class FrameTest {

public static void setUIFont(FontUIResource f) {

Enumeration keys = UIManager.getDefaults().keys();

while (keys.hasMoreElements()) {

Object key = keys.nextElement();

Object value = UIManager.get(key);

if (value instanceof FontUIResource) {

FontUIResource orig = (FontUIResource) value;

Font font = new Font(f.getFontName(), orig.getStyle(), f.getSize());

UIManager.put(key, new FontUIResource(font));

}

}

}

public static void main(String[] args) throws InterruptedException {

setUIFont(new FontUIResource(new Font("Arial", 0, 20)));

JFrame f = new JFrame("Demo");

f.getContentPane().setLayout(new BorderLayout());

JPanel p = new JPanel();

p.add(new JLabel("hello"));

p.setBorder(BorderFactory.createTitledBorder("Test Title"));

f.add(p);

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

f.setSize(300, 300);

f.setVisible(true);

}

}

生产：