TestLength.java

import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by liuchong on 2017/11/22.
 * Copyright(c) 2017 quanmincai Co., Ltd.
 * All right reserved.
 */
public class TestLength {
    public static void main(String[] args) throws Exception {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
        String message = "2017-11-18 23:46:37.940";
        Date date = sdf.parse(message);
        System.out.println(date.getTime());

        String message2 = "2017-11-18 23:46:38.021";
        Date date2 = sdf.parse(message2);
        System.out.println(date2.getTime());
        System.out.println(date2.getTime() - date.getTime());
    }
}