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package com.github.sylphlike.framework.utils.general;

import java.sql.Timestamp;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

/**
 * 高并发场景下System.currentTimeMillis()的性能问题的优化 调用方法；Clock.now();
 *   time 22/09/2020 14:10  星期二 (dd/MM/YYYY HH:mm)
 *  email [email protected]
 *
 *
 *
 * @author Gopal.pan
 * @version 1.0.0
 */
public class Clock {

    private final long period;
    private final AtomicLong now;

    private Clock(long period) {
        this.period = period;
        this.now = new AtomicLong(System.currentTimeMillis());
        scheduleClockUpdating();
    }

    private static Clock instance() {
        return InstanceHolder.INSTANCE;
    }

    public static long now() {
        return instance().currentTimeMillis();
    }

    public static String nowDate() {
        return new Timestamp(instance().currentTimeMillis()).toString();
    }

    private void scheduleClockUpdating() {
        ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor(runnable -> {
            Thread thread = new Thread(runnable, "System Clock");
            thread.setDaemon(true);
            return thread;
        });
        scheduler.scheduleAtFixedRate(() -> now.set(System.currentTimeMillis()), period, period, TimeUnit.MILLISECONDS);
    }

    private long currentTimeMillis() {
        return now.get();
    }

    private static class InstanceHolder {
        public static final Clock INSTANCE = new Clock(1);
    }
}