Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 org.apache.flink.runtime.util; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintStream; import java.net.Socket; import org.apache.commons.logging.Log; /** * An utility class for I/O related functionality. * */ public final class IOUtils { /** * The block size for byte operations in byte. */ private static final int BLOCKSIZE = 4096; /** * Private constructor to overwrite the public one. */ private IOUtils() { } /** * Copies from one stream to another. * * @param in * InputStream to read from * @param out * OutputStream to write to * @param buffSize * the size of the buffer * @param close * whether or not close the InputStream and OutputStream at the end. The streams are closed in the finally * clause. * @throws IOException * thrown if an error occurred while writing to the output stream */ public static void copyBytes(final InputStream in, final OutputStream out, final int buffSize, final boolean close) throws IOException { @SuppressWarnings("resource") final PrintStream ps = out instanceof PrintStream ? (PrintStream) out : null; final byte[] buf = new byte[buffSize]; try { int bytesRead = in.read(buf); while (bytesRead >= 0) { out.write(buf, 0, bytesRead); if ((ps != null) && ps.checkError()) { throw new IOException("Unable to write to output stream."); } bytesRead = in.read(buf); } } finally { if (close) { out.close(); in.close(); } } } /** * Copies from one stream to another. <strong>closes the input and output * streams at the end</strong>. * * @param in * InputStream to read from * @param out * OutputStream to write to * @throws IOException * thrown if an I/O error occurs while copying */ public static void copyBytes(final InputStream in, final OutputStream out) throws IOException { copyBytes(in, out, BLOCKSIZE, true); } /** * Copies from one stream to another. * * @param in * InputStream to read from * @param out * OutputStream to write to * @param close * whether or not close the InputStream and OutputStream at the * end. The streams are closed in the finally clause. * @throws IOException * thrown if an I/O error occurs while copying */ public static void copyBytes(final InputStream in, final OutputStream out, final boolean close) throws IOException { copyBytes(in, out, BLOCKSIZE, close); } /** * Reads len bytes in a loop. * * @param in * The InputStream to read from * @param buf * The buffer to fill * @param off * offset from the buffer * @param len * the length of bytes to read * @throws IOException * if it could not read requested number of bytes for any reason (including EOF) */ public static void readFully(final InputStream in, final byte[] buf, int off, final int len) throws IOException { int toRead = len; while (toRead > 0) { final int ret = in.read(buf, off, toRead); if (ret < 0) { throw new IOException("Premeture EOF from inputStream"); } toRead -= ret; off += ret; } } /** * Similar to readFully(). Skips bytes in a loop. * * @param in * The InputStream to skip bytes from * @param len * number of bytes to skip * @throws IOException * if it could not skip requested number of bytes for any reason (including EOF) */ public static void skipFully(final InputStream in, long len) throws IOException { while (len > 0) { final long ret = in.skip(len); if (ret < 0) { throw new IOException("Premeture EOF from inputStream"); } len -= ret; } } /** * Close the Closeable objects and <b>ignore</b> any {@link IOException} or * null pointers. Must only be used for cleanup in exception handlers. * * @param log * the log to record problems to at debug level. Can be <code>null</code>. * @param closeables * the objects to close */ public static void cleanup(final Log log, final java.io.Closeable... closeables) { for (java.io.Closeable c : closeables) { if (c != null) { try { c.close(); } catch (IOException e) { if (log != null && log.isDebugEnabled()) { log.debug("Exception in closing " + c, e); } } } } } /** * Closes the stream ignoring {@link IOException}. Must only be called in * cleaning up from exception handlers. * * @param stream * the stream to close */ public static void closeStream(final java.io.Closeable stream) { cleanup(null, stream); } /** * Closes the socket ignoring {@link IOException}. * * @param sock * the socket to close */ public static void closeSocket(final Socket sock) { // avoids try { close() } dance if (sock != null) { try { sock.close(); } catch (IOException ignored) { } } } }