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import java.lang.management.ManagementFactory;
 
public class Demo {
	public static void main(String... args) {
		final long uptime = ManagementFactory.getRuntimeMXBean().getUptime();
		System.out.println(String.format("Up for %dms", uptime));
	}
}

import java.lang.management.ManagementFactory;
import java.text.MessageFormat;
 
import org.joda.time.Period;
import org.joda.time.PeriodType;
import org.joda.time.format.PeriodFormatter;
import org.joda.time.format.PeriodFormatterBuilder;
 
public class Demo {
	public static void main(String... args) {
		final Period vmUptime = new Period(ManagementFactory.getRuntimeMXBean().getUptime()).normalizedStandard(PeriodType.yearDayTime());
		final PeriodFormatter pf = new PeriodFormatterBuilder()
				.printZeroAlways()
				.appendDays().appendLiteral(MessageFormat.format("{0,choice,0# days, |1# day, |2# days, }", vmUptime.getDays()))
				.minimumPrintedDigits(2)
				.appendHours().appendLiteral(":").appendMinutes()
				.toFormatter();
		System.out.println(String.format("Up for %s", pf.print(vmUptime)));
	}
}