java中每24小时或一天只调用一次函数的逻辑

Question

i have one function

callEach24hourOneTime();

i have to call this function in each 24 hour only one time within 24 once it will executed then i don't have to call callEach24hourOneTime

i am unable to get current time hour minute and second in millis so that i can apply condition i tried below logic but unable to execute.

if(currentmillis=86400000 ){
 callEach24hourOneTime(); 
}
else {
//dont call do other operation
}

please suggest me solution for this .

Answer 1

Logic to always have at least 24 hours between executions of the callEach24hourOneTime() method:

private long nextCallMillis;

long currentMillis = System.currentTimeMillis();
if (currentMillis >= this.nextCallMillis) {
    this.nextCallMillis = currentMillis + 86400000/*24 hours*/;
    callEach24hourOneTime();
} else {
    // ...
}

That will cause a drift in time-of-day for the execution of the method. The speed of the drift is determined by how often the code is execute.

If you instead want method to be called at (around) the same time every day :

private long nextCallMillis;

long currentMillis = System.currentTimeMillis();
if (this.nextCallMillis == 0)
    this.nextCallMillis = currentMillis; // Establish time-of-day
if (currentMillis >= this.nextCallMillis) {
    this.nextCallMillis += ((currentMillis - this.nextCallMillis) / 86400000 + 1) * 86400000;
    callEach24hourOneTime();
} else {
    // ...
}

"Same time every day" is in UTC, so when crossing Daylight Savings Time changes, the time-of-day will change by 1 hour.

---

UPDATE

If you just want "once per day" logic:

private LocalDate lastCallDate;

LocalDate today = LocalDate.now();
if (! today.equals(lastCallDate)) {
    this.lastCallDate = today;
    callOnceDailyOneTime();
} else {
    // ...
}

Answer 2

You can you a cron library.

I don't really know what language or framework you are currently using, but from spring I'd say you can use @Scheduled :

@Scheduled(cron = "0 0 0 * * *")
  private void myMethod(){}

For exemple the cron above will make myMethod() execute once a day.