Here you can find the source of listFiles(String path, String extension)
public static String[] listFiles(String path, String extension) throws IOException
//package com.java2s; /*// ww w . j a v a2 s . c o m * Copyright 2015 Futeh Kao * * Licensed 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 * * http://www.apache.org/licenses/LICENSE-2.0 * * 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.io.File; import java.io.IOException; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; import java.util.LinkedList; import java.util.List; import java.util.stream.Stream; public class Main { private static final String[] EMPTY_FILE_LIST = new String[0]; public static String[] listFiles(String path, String extension) throws IOException { String[] paths = EMPTY_FILE_LIST; if (path.endsWith("**")) { String dir = path.substring(0, path.length() - 2); if (Paths.get(dir).toFile().isDirectory()) { paths = listFiles(dir, extension, true); } else if (!Paths.get(dir).toFile().exists()) { throw new IOException("Directory " + dir + " does not exist"); } } else if (path.endsWith("*")) { String dir = path.substring(0, path.length() - 1); if (Paths.get(dir).toFile().isDirectory()) { paths = listFiles(dir, extension, false); } else if (!Paths.get(dir).toFile().exists()) { throw new IOException("Directory " + dir + " does not exist"); } } else { paths = getSingleFile(path, extension); } return paths; } private static String[] listFiles(String path, String extension, boolean recursive) throws IOException { List<String> directories = new LinkedList<>(); List<String> list = new LinkedList<>(); if (new File(path).isDirectory()) { // a directory directories.add(path); } else if (extension == null || path.endsWith(extension)) { list.add(path); } while (!directories.isEmpty()) { String parent = directories.remove(0); try (Stream<Path> stream = Files.list(Paths.get(parent))) { stream.forEach(f -> { if (f.toFile().isDirectory()) { if (recursive) directories.add(f.toString()); } else if (extension == null || f.toString().endsWith(extension)) { list.add(f.toString()); } }); } } return list.toArray(new String[list.size()]); } private static String[] getSingleFile(String path, String extension) { String p = path.endsWith(extension) ? path : path + extension; if (path.startsWith("classpath:")) { return new String[] { p }; } else { File f = new File(p); if (!f.isDirectory() && f.exists()) return new String[] { p }; return EMPTY_FILE_LIST; } } }