Scheduling a task to happen at a specific time (in Java)

Question

I have already looked at the forum for this and I kind of got the answer, but it didn't quite fit my problem.

So the thing is (this is for a college assignment): I have to schedule a task to happen at a specific time in the future (to be defined by the user of the program).

First I started trying to get this working by choosing a date this way:

//this is my main class

        DateFormat dateFormatter = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
        String year = String.valueOf(LocalDate.now().getYear());
        String month = String.valueOf(LocalDate.now().getMonthValue());
        String day = "05";
        Date date = dateFormatter.parse(year + "-" + month + "-" + day + " 02:24:08");

        Timer timer = new Timer();
        timer.schedule(new MyTimeTask("Patrick"), date);

//the class MyTimeTask:

        public class MyTimeTask extends TimerTask {
           private String name;
           public MyTimeTask(String name) {
              this.name = name;
           }
           public void run() {
              System.out.println(this.name);
           }
        }

The problem is: this doesn't run at the time I want. Instead, it automatically runs as soon as I run the file, no matter how far in the future I choose the date.

Where am I wrong?

Thank you.

Answer 1

You have a couple problems in your code that need addressed.

First is this: new SimpleDateFormat("yyyy-mm-dd hh:mm:ss"). Take a closer look at your pattern. yyyy-mm-dd hh:mm:ss translates to year-minute-day hour:minute:second. I believe you want the month after the year, not the minute. A simple change to yyyy-MM-dd hh:mm:ss fixes that.

Second, LocalDate.now().getMonthValue() is (at the moment) returning 6 (instead of 06), so your pattern yyyy:MM:dd does not match it. To fix this, I would combine your year and month strings into a single variable so you can use DateTimeFormatter to format the month as MM:

String yearMonth = LocalDate.now().format(DateTimeFormatter.ofPattern("yyyy-MM"));

Now you can parse your date like this:

Date date = dateFormatter.parse(yearMonth + "-" + day + " 02:24:08");

The last thing I would do (this is not completely necessary) is to specify whether the given time is ante meridian or post meridian, or change the hour to military time. To do this you can just add "aa" to end of your date formatter.

Here's the final code:

DateFormat dateFormatter = new SimpleDateFormat("yyyy-MM-dd hh:mm:ssaa");
String yearMonth = LocalDate.now().format(DateTimeFormatter.ofPattern("yyyy-MM"));
String day = "04";
Date date = dateFormatter.parse(yearMonth + "-" + day + " 02:24:08PM");

Timer timer = new Timer();
timer.schedule(new MyTimeTask("Patrick"), date);