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.commons.io; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.io.Reader; import java.io.StringReader; import java.io.Writer; /** * This class provides static utility methods for buffered * copying between sources (<code>InputStream</code>, <code>Reader</code>, * <code>String</code> and <code>byte[]</code>) and destinations * (<code>OutputStream</code>, <code>Writer</code>, <code>String</code> and * <code>byte[]</code>). * <p> * Unless otherwise noted, these <code>copy</code> methods do <em>not</em> * flush or close the streams. Often doing so would require making non-portable * assumptions about the streams' origin and further use. This means that both * streams' <code>close()</code> methods must be called after copying. if one * omits this step, then the stream resources (sockets, file descriptors) are * released when the associated Stream is garbage-collected. It is not a good * idea to rely on this mechanism. For a good overview of the distinction * between "memory management" and "resource management", see * <a href="http://www.unixreview.com/articles/1998/9804/9804ja/ja.htm">this * UnixReview article</a>. * <p> * For byte-to-char methods, a <code>copy</code> variant allows the encoding * to be selected (otherwise the platform default is used). We would like to * encourage you to always specify the encoding because relying on the platform * default can lead to unexpected results. * <p * We don't provide special variants for the <code>copy</code> methods that * let you specify the buffer size because in modern VMs the impact on speed * seems to be minimal. We're using a default buffer size of 4 KB. * <p> * The <code>copy</code> methods use an internal buffer when copying. It is * therefore advisable <em>not</em> to deliberately wrap the stream arguments * to the <code>copy</code> methods in <code>Buffered*</code> streams. For * example, don't do the following: * <pre> * copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) ); * </pre> * The rationale is as follows: * <p> * Imagine that an InputStream's read() is a very expensive operation, which * would usually suggest wrapping in a BufferedInputStream. The * BufferedInputStream works by issuing infrequent * {@link java.io.InputStream#read(byte[] b, int off, int len)} requests on the * underlying InputStream, to fill an internal buffer, from which further * <code>read</code> requests can inexpensively get their data (until the buffer * runs out). * <p> * However, the <code>copy</code> methods do the same thing, keeping an * internal buffer, populated by * {@link InputStream#read(byte[] b, int off, int len)} requests. Having two * buffers (or three if the destination stream is also buffered) is pointless, * and the unnecessary buffer management hurts performance slightly (about 3%, * according to some simple experiments). * <p> * Behold, intrepid explorers; a map of this class: * <pre> * Method Input Output Dependency * ------ ----- ------ ------- * 1 copy InputStream OutputStream (primitive) * 2 copy Reader Writer (primitive) * * 3 copy InputStream Writer 2 * * 4 copy Reader OutputStream 2 * * 5 copy String OutputStream 2 * 6 copy String Writer (trivial) * * 7 copy byte[] Writer 3 * 8 copy byte[] OutputStream (trivial) * </pre> * <p> * Note that only the first two methods shuffle bytes; the rest use these * two, or (if possible) copy using native Java copy methods. As there are * method variants to specify the encoding, each row may * correspond to up to 2 methods. * <p> * Origin of code: Excalibur. * * @author Peter Donald * @author Jeff Turner * @author Matthew Hawthorne * @version $Id: CopyUtils.java 437680 2006-08-28 11:57:00Z scolebourne $ * @deprecated Use IOUtils. Will be removed in 2.0. * Methods renamed to IOUtils.write() or IOUtils.copy(). * Null handling behaviour changed in IOUtils (null data does not * throw NullPointerException). */ public class CopyUtils { /** * The default size of the buffer. */ private static final int DEFAULT_BUFFER_SIZE = 1024 * 4; /** * Instances should NOT be constructed in standard programming. */ public CopyUtils() { } // ---------------------------------------------------------------- // byte[] -> OutputStream // ---------------------------------------------------------------- /** * Copy bytes from a <code>byte[]</code> to an <code>OutputStream</code>. * @param input the byte array to read from * @param output the <code>OutputStream</code> to write to * @throws IOException In case of an I/O problem */ public static void copy(byte[] input, OutputStream output) throws IOException { output.write(input); } // ---------------------------------------------------------------- // byte[] -> Writer // ---------------------------------------------------------------- /** * Copy and convert bytes from a <code>byte[]</code> to chars on a * <code>Writer</code>. * The platform's default encoding is used for the byte-to-char conversion. * @param input the byte array to read from * @param output the <code>Writer</code> to write to * @throws IOException In case of an I/O problem */ public static void copy(byte[] input, Writer output) throws IOException { ByteArrayInputStream in = new ByteArrayInputStream(input); copy(in, output); } /** * Copy and convert bytes from a <code>byte[]</code> to chars on a * <code>Writer</code>, using the specified encoding. * @param input the byte array to read from * @param output the <code>Writer</code> to write to * @param encoding The name of a supported character encoding. See the * <a href="http://www.iana.org/assignments/character-sets">IANA * Charset Registry</a> for a list of valid encoding types. * @throws IOException In case of an I/O problem */ public static void copy(byte[] input, Writer output, String encoding) throws IOException { ByteArrayInputStream in = new ByteArrayInputStream(input); copy(in, output, encoding); } // ---------------------------------------------------------------- // Core copy methods // ---------------------------------------------------------------- /** * Copy bytes from an <code>InputStream</code> to an * <code>OutputStream</code>. * @param input the <code>InputStream</code> to read from * @param output the <code>OutputStream</code> to write to * @return the number of bytes copied * @throws IOException In case of an I/O problem */ public static int copy(InputStream input, OutputStream output) throws IOException { byte[] buffer = new byte[DEFAULT_BUFFER_SIZE]; int count = 0; int n = 0; while (-1 != (n = input.read(buffer))) { output.write(buffer, 0, n); count += n; } return count; } // ---------------------------------------------------------------- // Reader -> Writer // ---------------------------------------------------------------- /** * Copy chars from a <code>Reader</code> to a <code>Writer</code>. * @param input the <code>Reader</code> to read from * @param output the <code>Writer</code> to write to * @return the number of characters copied * @throws IOException In case of an I/O problem */ public static int copy(Reader input, Writer output) throws IOException { char[] buffer = new char[DEFAULT_BUFFER_SIZE]; int count = 0; int n = 0; while (-1 != (n = input.read(buffer))) { output.write(buffer, 0, n); count += n; } return count; } // ---------------------------------------------------------------- // InputStream -> Writer // ---------------------------------------------------------------- /** * Copy and convert bytes from an <code>InputStream</code> to chars on a * <code>Writer</code>. * The platform's default encoding is used for the byte-to-char conversion. * @param input the <code>InputStream</code> to read from * @param output the <code>Writer</code> to write to * @throws IOException In case of an I/O problem */ public static void copy(InputStream input, Writer output) throws IOException { InputStreamReader in = new InputStreamReader(input); copy(in, output); } /** * Copy and convert bytes from an <code>InputStream</code> to chars on a * <code>Writer</code>, using the specified encoding. * @param input the <code>InputStream</code> to read from * @param output the <code>Writer</code> to write to * @param encoding The name of a supported character encoding. See the * <a href="http://www.iana.org/assignments/character-sets">IANA * Charset Registry</a> for a list of valid encoding types. * @throws IOException In case of an I/O problem */ public static void copy(InputStream input, Writer output, String encoding) throws IOException { InputStreamReader in = new InputStreamReader(input, encoding); copy(in, output); } // ---------------------------------------------------------------- // Reader -> OutputStream // ---------------------------------------------------------------- /** * Serialize chars from a <code>Reader</code> to bytes on an * <code>OutputStream</code>, and flush the <code>OutputStream</code>. * @param input the <code>Reader</code> to read from * @param output the <code>OutputStream</code> to write to * @throws IOException In case of an I/O problem */ public static void copy(Reader input, OutputStream output) throws IOException { OutputStreamWriter out = new OutputStreamWriter(output); copy(input, out); // XXX Unless anyone is planning on rewriting OutputStreamWriter, we // have to flush here. out.flush(); } // ---------------------------------------------------------------- // String -> OutputStream // ---------------------------------------------------------------- /** * Serialize chars from a <code>String</code> to bytes on an * <code>OutputStream</code>, and * flush the <code>OutputStream</code>. * @param input the <code>String</code> to read from * @param output the <code>OutputStream</code> to write to * @throws IOException In case of an I/O problem */ public static void copy(String input, OutputStream output) throws IOException { StringReader in = new StringReader(input); OutputStreamWriter out = new OutputStreamWriter(output); copy(in, out); // XXX Unless anyone is planning on rewriting OutputStreamWriter, we // have to flush here. out.flush(); } // ---------------------------------------------------------------- // String -> Writer // ---------------------------------------------------------------- /** * Copy chars from a <code>String</code> to a <code>Writer</code>. * @param input the <code>String</code> to read from * @param output the <code>Writer</code> to write to * @throws IOException In case of an I/O problem */ public static void copy(String input, Writer output) throws IOException { output.write(input); } }