Java Timer 疑問

想請教 Java Timer 兩個 method 有咩分別

之前用開 method (1) ，個 runnable 跑跑吓會 shift 咗個時間，例如我有個 runnable 9:00:00am start。開頭十零廿次都差不多係00秒開始，但久而久之個一頭遲開始。

Google 過有人話用 method (2) , 但都係有 shift 的情況

Timer timer = new Timer();
(1) timer.scheduleAtFixedRate(...)
(2) timer.schedule(...)

想問問 (1) 同 (2) 有咩分別，點樣先可以 ensure 到 d Runnable 真係踏正 00秒就跑?

謝謝

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KinChungE

長老會員

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2^#

發表於 2022-6-16 21:36 | 只看該作者

Timer本身設計唔係高precision, 一定行得越耐shift得越勁
不論Java / C# / JS等都係咁

你要D野指定果一秒內做, 應該schedule住個task每秒都行幾次
每次run都check住system clock夠鐘未, 夠鐘就做野

再唔係就用OS既task scheduler

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zeroho

中級會員

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3^#

發表於 2022-6-18 01:43 | 只看該作者

今日試咗每秒行一次呢個 approach 踏正 00 就跑，不過發現佢會久唔欠有1分鐘的00秒行幾次同一個動作。睇 code 未睇到原因

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zeroho

中級會員

Rank: 2 Rank: 2

4^#

發表於 2022-6-18 01:46 | 只看該作者

我個 Runnable 每踏正00/10/20/30/40/50秒就跑，間唔中會有1下跑多幾次。
[2022-06-17 14:10:20.020] Completed copying 604604 transactions ...: 3 ms
[2022-06-17 14:10:30.030] Completed copying 604604 transactions ...: 2 ms
[2022-06-17 14:10:40.040] Completed copying 604604 transactions ...: 2 ms
[2022-06-17 14:10:50.050] Completed copying 604604 transactions ...: 3 ms
[2022-06-17 14:11:00.000] Completed copying 604604 transactions ...: 4 ms
[2022-06-17 14:11:20.020] Completed copying 608044 transactions ...: 3 ms
[2022-06-17 14:11:20.020] Completed copying 608044 transactions ...: 2 ms
[2022-06-17 14:11:20.020] Completed copying 608044 transactions ...: 2 ms
[2022-06-17 14:11:20.020] Completed copying 608044 transactions ...: 2 ms
[2022-06-17 14:11:20.020] Completed copying 608044 transactions ...: 2 ms
[2022-06-17 14:11:30.030] Completed copying 608044 transactions ...: 3 ms
[2022-06-17 14:11:40.040] Completed copying 608044 transactions ...: 2 ms
[2022-06-17 14:11:50.050] Completed copying 608044 transactions ...: 3 ms
[2022-06-17 14:12:00.000] Completed copying 608044 transactions ...: 2 ms

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zeroho