Here you can find the source of uuid()
public static String uuid()
//package com.java2s; /**//from w ww .j a v a 2s. c o m * Copyright 2016 benjobs * <p> * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * <p> * http://www.apache.org/licenses/LICENSE-2.0 * <p> * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. */ import java.util.*; public class Main { public static String uuid() { return UUID.randomUUID().toString().replaceAll("-", ""); } public static String uuid(int len) { StringBuffer sb = new StringBuffer(); while (sb.length() < len) { sb.append(uuid()); } return sb.toString().substring(0, len); } }