Java tutorial
/* * Copyright 2012 Alex Holmes * * 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. */ package com.alexholmes.hadooputils.io; import org.apache.commons.io.IOUtils; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.util.Collection; import java.util.List; /** * Utilities to help work with files in Hadoop file systems. */ public final class FileUtils { /** * Private ctor to prevent instantiation. */ private FileUtils() { } /** * Read the contents of the supplied file into a list. * * @param fs a Hadoop file system * @param p the file path * @return array of lines in the file * @throws java.io.IOException if something goes wrong */ public static List<String> readLines(final FileSystem fs, final Path p) throws IOException { InputStream stream = fs.open(p); try { return IOUtils.readLines(stream); } finally { stream.close(); } } /** * Writes the array list into a file as newline-separated lines. * * @param fs a Hadoop file system * @param p the file path * @return array of lines to write to the file * @throws java.io.IOException if something goes wrong */ public static void writeLines(Collection<?> lines, final FileSystem fs, final Path p) throws IOException { OutputStream stream = fs.create(p); try { IOUtils.writeLines(lines, IOUtils.LINE_SEPARATOR, stream); } finally { stream.close(); } } }