How to convert milliseconds into hours and days?

Question

I want to get the JVM start time and uptime. So far I have done this:

public long getjvmstarttime(){
    final long uptime = ManagementFactory.getRuntimeMXBean().getStartTime();
    return uptime;
}

public long getjvmuptime(){
    final long uptime = ManagementFactory.getRuntimeMXBean().getUptime();
    return uptime;
}

But I get the time in milliseconds. How I can convert the time in days and hours. I want to display the milliseconds in this format: 3 days, 8 hours, 32 minutes. Is there amy internal Java method that can convert the milliseconds?

Answer 1

Once you have the time in milliseconds you can use the TimeUnit enum to convert it to other time units. Converting to days will just require one call.

long days = TimeUnit.MILLISECONDS.toDays(milliseconds);

Getting the hours will involve another similar call for the total hours, then computing the left over hours after the days are subtracted out.

Answer 2

The code below does the math you need and builds the resulting string:

private static final int SECOND = 1000;
private static final int MINUTE = 60 * SECOND;
private static final int HOUR = 60 * MINUTE;
private static final int DAY = 24 * HOUR;

// TODO: this is the value in ms
long ms = 10304004543l;
StringBuffer text = new StringBuffer("");
if (ms > DAY) {
  text.append(ms / DAY).append(" days ");
  ms %= DAY;
}
if (ms > HOUR) {
  text.append(ms / HOUR).append(" hours ");
  ms %= HOUR;
}
if (ms > MINUTE) {
  text.append(ms / MINUTE).append(" minutes ");
  ms %= MINUTE;
}
if (ms > SECOND) {
  text.append(ms / SECOND).append(" seconds ");
  ms %= SECOND;
}
text.append(ms + " ms");
System.out.println(text.toString());