如何获得 a 的默认边框JButton?
一个例子是:
Border border = new JButton().getBorder();
但是我可以在不创建新按钮的情况下做到这一点吗?
您可以从以下位置检索默认边框UIManager:
UIManager.getBorder("Button.border");
例如:
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
public class TestButton {
    private static void createAndShowGUI() {
        JFrame frame = new JFrame("TestButton");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JButton button = new JButton("Click");
        button.setBorder(BorderFactory.createLineBorder(Color.BLACK, 2));
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                ((JButton)e.getSource()).setBorder(UIManager.getBorder("Button.border"));
            }
        });
        frame.add(button);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}