FileListing.java

/**
 * Copyright (c) 2011, SOCIETIES Consortium (WATERFORD INSTITUTE OF TECHNOLOGY (TSSG), HERIOT-WATT UNIVERSITY (HWU), SOLUTA.NET 
 * (SN), GERMAN AEROSPACE CENTRE (Deutsches Zentrum fuer Luft- und Raumfahrt e.V.) (DLR), Zavod za varnostne tehnologije
 * informacijske družbe in elektronsko poslovanje (SETCCE), INSTITUTE OF COMMUNICATION AND COMPUTER SYSTEMS (ICCS), LAKE
 * COMMUNICATIONS (LAKE), INTEL PERFORMANCE LEARNING SOLUTIONS LTD (INTEL), PORTUGAL TELECOM INOVAÇÃO, SA (PTIN), IBM Corp., 
 * INSTITUT TELECOM (ITSUD), AMITEC DIACHYTI EFYIA PLIROFORIKI KAI EPIKINONIES ETERIA PERIORISMENIS EFTHINIS (AMITEC), TELECOM 
 * ITALIA S.p.a.(TI),  TRIALOG (TRIALOG), Stiftelsen SINTEF (SINTEF), NEC EUROPE LTD (NEC))
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
 * conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
 *    disclaimer in the documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT 
 * SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.societies.maven;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * Recursive file listing under a specified directory.
 */
public final class FileListing {
	
	/**
	 * Recursively walk a directory tree and return a List of all Files found;
	 * the List is sorted using File.compareTo().
	 * 
	 * @param aStartingDir
	 *            is a valid directory, which can be read.
	 */
	static public List<File> getFileListing(File aStartingDir) throws FileNotFoundException {
		validateDirectory(aStartingDir);
		List<File> result = getFileListingNoSort(aStartingDir);
		Collections.sort(result);
		return result;
	}

	static private List<File> getFileListingNoSort(File aStartingDir) throws FileNotFoundException {
		List<File> result = new ArrayList<File>();
		File[] filesAndDirs = aStartingDir.listFiles();
		List<File> filesDirs = Arrays.asList(filesAndDirs);
		for (File file : filesDirs) {
			result.add(file);
			if (!file.isFile()) {
				List<File> deeperList = getFileListingNoSort(file);
				result.addAll(deeperList);
			}
		}
		return result;
	}

	static private void validateDirectory(File aDirectory) throws FileNotFoundException {
		if (aDirectory == null) {
			throw new IllegalArgumentException("Directory should not be null.");
		}
		if (!aDirectory.exists()) {
			throw new FileNotFoundException("Directory does not exist: " + aDirectory);
		}
		if (!aDirectory.isDirectory()) {
			throw new IllegalArgumentException("Is not a directory: " + aDirectory);
		}
		if (!aDirectory.canRead()) {
			throw new IllegalArgumentException("Directory cannot be read: " + aDirectory);
		}
	}
}