public static void main(String[] args) {


    long time1 = 1619598540;
    String result1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(time1*1000);
    System.out.println("---10位数的时间戳（毫秒）--->Date:" + result1);



    double time2 = 1619597640000d;
    String result2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(time2);
    System.out.println("---13位数的时间戳（毫秒）--->Date:" + result2);


}



注意10位*个1000