001/* 002 * #%L 003 * Netarchivesuite - common 004 * %% 005 * Copyright (C) 2005 - 2014 The Royal Danish Library, the Danish State and University Library, 006 * the National Library of France and the Austrian National Library. 007 * %% 008 * This program is free software: you can redistribute it and/or modify 009 * it under the terms of the GNU Lesser General Public License as 010 * published by the Free Software Foundation, either version 2.1 of the 011 * License, or (at your option) any later version. 012 * 013 * This program is distributed in the hope that it will be useful, 014 * but WITHOUT ANY WARRANTY; without even the implied warranty of 015 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 016 * GNU General Lesser Public License for more details. 017 * 018 * You should have received a copy of the GNU General Lesser Public 019 * License along with this program. If not, see 020 * <http://www.gnu.org/licenses/lgpl-2.1.html>. 021 * #L% 022 */ 023 024package dk.netarkivet.common.utils; 025 026import java.io.File; 027import java.util.Arrays; 028 029/** 030 * An iterator that iterates over elements that can be read from files, given an array of files. It is robust against 031 * disappearing files, but does not try to find new ones that appear while iterating. It keeps the Iterator contract 032 * that next() returns an element if hasNext() returned true since last next(). This may mean that the underlying file 033 * has disappeared by the time next() is called, but the object is returned anyway. 034 * 035 * @param <T> The type returned by the FileArrayIterator 036 */ 037public abstract class FileArrayIterator<T> extends FilterIterator<File, T> { 038 039 protected FileArrayIterator(File[] files) { 040 super(Arrays.asList(files).iterator()); 041 } 042 043 /** 044 * Returns the T object corresponding to the given file, or null if that object is to be skipped. 045 * 046 * @param f A given file 047 * @return An object in the T domain, or null 048 */ 049 protected T filter(File f) { 050 return getNext(f); 051 } 052 053 /** 054 * Gives an object created from the given file, or null. 055 * 056 * @param file The file to read 057 * @return An object of the type iterated over by the list, or null if the file does not exist or cannot be used to 058 * create an appropriate object. 059 */ 060 protected abstract T getNext(final File file); 061 062}