Here you can find the source of sleep(long millis)
public static void sleep(long millis)
//package com.java2s; //License from project: Apache License import java.util.concurrent.TimeUnit; public class Main { public static void sleep(long millis) { sleep(millis, TimeUnit.MILLISECONDS); }//www . j a v a 2s . com private static void sleep(long amount, TimeUnit unit) { try { Thread.sleep(unit.toMillis(amount) * getTimeFactor()); } catch (InterruptedException e) { // Ignore it. } } public static int getTimeFactor() { return Integer.getInteger("time.factor", 1); } }