java - AtomicInteger Class Inconsistency -

i using atomicinteger class increment value of customerid , productid. dont have database using serialization store state of application , command based application. everytime add customer or product costructor calls idgenerateor class has atomicinteger create id. there inconsistency, somtimes increment id , not, tell me whats wrong.

public final class idgenerator implements serializable {   private static atomicinteger nextid = new atomicinteger();    public static int newid()    {     return nextid.incrementandget();   } }    public customer (string name, string email, string phone, address address)  {     this.name = name;     this.email = email;     this.phone = phone.replaceall("[\\s\\-()]", ""); // drop non-digit characters     this.address = address;     this.id = idgenerator.newid();     this.facebook="";     this.twitter="";     this.deliveryinstructions=""; }