Here you can find the source of sleep(final long millis)
public static boolean sleep(final long millis)
//package com.java2s; //License from project: Apache License public class Main { public static boolean sleep(final long millis) { try {/* w w w.jav a2 s .c o m*/ if (millis > 0) { Thread.sleep(millis); } } catch (final InterruptedException e) { Thread.currentThread().interrupt(); // It's not an error that we were Interrupted!! Don't log the // exception ! return false; } return true; } }