Java/com/study/demo11/TimeViewer.java

package com.study.demo11;

import java.awt.Frame;
import java.awt.Label;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class TimeViewer extends Frame {
    private Label timeLabel;
    private DateTimeFormatter formatter;

    public TimeViewer() {
        super("系统时间显示器");
        formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

        timeLabel = new Label("", Label.CENTER);
        add(timeLabel);

        setSize(300, 100);
        setLayout(new java.awt.FlowLayout());
        setLocationRelativeTo(null);
        setVisible(true);

        updateTime();
        startTimeUpdate();
    }

    private void updateTime() {
        LocalDateTime now = LocalDateTime.now();
        timeLabel.setText(now.format(formatter));
    }

    private void startTimeUpdate() {
        new java.util.Timer().scheduleAtFixedRate(new java.util.TimerTask() {
            @Override
            public void run() {
                updateTime();
            }
        }, 0, 1000);
    }

    public static void main(String[] args) {
        new TimeViewer();
    }
}