在JTextField上单击或按TAB键时选择所有文本

import javax.swing.*;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;

public class Main {
    public static void main(String[] args) {
        JFrame frame = new JFrame("JTextField Example");
        JTextField textField = new JTextField();
        textField.setBounds(50, 50, 200, 30);

        textField.addFocusListener(new FocusAdapter() {
            @Override
            public void focusGained(FocusEvent e) {
                textField.selectAll();
            }
        });

        frame.add(textField);
        frame.setSize(300, 200);
        frame.setLayout(null);
        frame.setVisible(true);
    }
}