Here you can find the source of getSequenceNumber()
public static String getSequenceNumber()
//package com.java2s; //License from project: Open Source License import java.util.concurrent.atomic.AtomicLong; public class Main { private static final AtomicLong atomicLong = new AtomicLong(0); public static String getSequenceNumber() { long id = atomicLong.addAndGet(1); return String.valueOf(id); }/* w w w. j a v a 2 s.c o m*/ }