如何在当前java程序窗口之外获取所选文本？

import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.StringSelection;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;

public class GetSelectedText {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Get Selected Text Example");
        JTextField textField = new JTextField();
        JButton button = new JButton("Copy Selected Text");

        button.addActionListener(e -> {
            String selectedText = textField.getSelectedText();
            Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
            StringSelection selection = new StringSelection(selectedText);
            clipboard.setContents(selection, null);
        });

        frame.getContentPane().add(textField);
        frame.getContentPane().add(button);
        frame.setLayout(new FlowLayout());
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}