Here you can find the source of touch(File file)
public static void touch(File file) throws IOException
//package com.java2s; /*//from w w w .j a v a 2s . com * Distributed as part of mchange-commons-java 0.2.9 * * Copyright (C) 2015 Machinery For Change, Inc. * * Author: Steve Waldman <swaldman@mchange.com> * * This library is free software; you can redistribute it and/or modify * it under the terms of EITHER: * * 1) The GNU Lesser General Public License (LGPL), version 2.1, as * published by the Free Software Foundation * * OR * * 2) The Eclipse Public License (EPL), version 1.0 * * You may choose which license to accept if you wish to redistribute * or modify this work. You may offer derivatives of this work * under the license you have chosen, or you may provide the same * choice of license which you have been offered here. * * This software is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. * * You should have received copies of both LGPL v2.1 and EPL v1.0 * along with this software; see the files LICENSE-EPL and LICENSE-LGPL. * If not, the text of these licenses are currently available at * * LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html * EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php * */ import java.io.*; public class Main { public static void touch(File file) throws IOException { if (!file.exists()) createEmpty(file); unguardedTouch(file); } public static void createEmpty(File file) throws IOException { RandomAccessFile raf = null; try { raf = new RandomAccessFile(file, "rws"); raf.setLength(0); } finally { try { if (raf != null) raf.close(); } catch (IOException e) { e.printStackTrace(); } } } private static void unguardedTouch(File file) throws IOException { file.setLastModified(System.currentTimeMillis()); } }