Java tutorial
/* * Copyright (c) 1996, 2016, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.io; import java.nio.CharBuffer; import java.nio.charset.Charset; import java.nio.charset.CharsetEncoder; import sun.nio.cs.StreamEncoder; /** * An OutputStreamWriter is a bridge from character streams to byte streams: * Characters written to it are encoded into bytes using a specified {@link * java.nio.charset.Charset charset}. The charset that it uses * may be specified by name or may be given explicitly, or the platform's * default charset may be accepted. * * <p> Each invocation of a write() method causes the encoding converter to be * invoked on the given character(s). The resulting bytes are accumulated in a * buffer before being written to the underlying output stream. Note that the * characters passed to the write() methods are not buffered. * * <p> For top efficiency, consider wrapping an OutputStreamWriter within a * BufferedWriter so as to avoid frequent converter invocations. For example: * * <pre> * Writer out * = new BufferedWriter(new OutputStreamWriter(System.out)); * </pre> * * <p> A <i>surrogate pair</i> is a character represented by a sequence of two * {@code char} values: A <i>high</i> surrogate in the range '\uD800' to * '\uDBFF' followed by a <i>low</i> surrogate in the range '\uDC00' to * '\uDFFF'. * * <p> A <i>malformed surrogate element</i> is a high surrogate that is not * followed by a low surrogate or a low surrogate that is not preceded by a * high surrogate. * * <p> This class always replaces malformed surrogate elements and unmappable * character sequences with the charset's default <i>substitution sequence</i>. * The {@linkplain java.nio.charset.CharsetEncoder} class should be used when more * control over the encoding process is required. * * @see BufferedWriter * @see OutputStream * @see java.nio.charset.Charset * * @author Mark Reinhold * @since 1.1 */ public class OutputStreamWriter extends Writer { private final StreamEncoder se; /** * Creates an OutputStreamWriter that uses the named charset. * * @param out * An OutputStream * * @param charsetName * The name of a supported * {@link java.nio.charset.Charset charset} * * @exception UnsupportedEncodingException * If the named encoding is not supported */ public OutputStreamWriter(OutputStream out, String charsetName) throws UnsupportedEncodingException { super(out); if (charsetName == null) throw new NullPointerException("charsetName"); se = StreamEncoder.forOutputStreamWriter(out, this, charsetName); } /** * Creates an OutputStreamWriter that uses the default character encoding. * * @param out An OutputStream */ public OutputStreamWriter(OutputStream out) { super(out); try { se = StreamEncoder.forOutputStreamWriter(out, this, (String) null); } catch (UnsupportedEncodingException e) { throw new Error(e); } } /** * Creates an OutputStreamWriter that uses the given charset. * * @param out * An OutputStream * * @param cs * A charset * * @since 1.4 * @spec JSR-51 */ public OutputStreamWriter(OutputStream out, Charset cs) { super(out); if (cs == null) throw new NullPointerException("charset"); se = StreamEncoder.forOutputStreamWriter(out, this, cs); } /** * Creates an OutputStreamWriter that uses the given charset encoder. * * @param out * An OutputStream * * @param enc * A charset encoder * * @since 1.4 * @spec JSR-51 */ public OutputStreamWriter(OutputStream out, CharsetEncoder enc) { super(out); if (enc == null) throw new NullPointerException("charset encoder"); se = StreamEncoder.forOutputStreamWriter(out, this, enc); } /** * Returns the name of the character encoding being used by this stream. * * <p> If the encoding has an historical name then that name is returned; * otherwise the encoding's canonical name is returned. * * <p> If this instance was created with the {@link * #OutputStreamWriter(OutputStream, String)} constructor then the returned * name, being unique for the encoding, may differ from the name passed to * the constructor. This method may return {@code null} if the stream has * been closed. </p> * * @return The historical name of this encoding, or possibly * <code>null</code> if the stream has been closed * * @see java.nio.charset.Charset * * @revised 1.4 * @spec JSR-51 */ public String getEncoding() { return se.getEncoding(); } /** * Flushes the output buffer to the underlying byte stream, without flushing * the byte stream itself. This method is non-private only so that it may * be invoked by PrintStream. */ void flushBuffer() throws IOException { se.flushBuffer(); } /** * Writes a single character. * * @exception IOException If an I/O error occurs */ public void write(int c) throws IOException { se.write(c); } /** * Writes a portion of an array of characters. * * @param cbuf Buffer of characters * @param off Offset from which to start writing characters * @param len Number of characters to write * * @throws IndexOutOfBoundsException * If {@code off} is negative, or {@code len} is negative, * or {@code off + len} is negative or greater than the length * of the given array * * @throws IOException If an I/O error occurs */ public void write(char cbuf[], int off, int len) throws IOException { se.write(cbuf, off, len); } /** * Writes a portion of a string. * * @param str A String * @param off Offset from which to start writing characters * @param len Number of characters to write * * @throws IndexOutOfBoundsException * If {@code off} is negative, or {@code len} is negative, * or {@code off + len} is negative or greater than the length * of the given string * * @throws IOException If an I/O error occurs */ public void write(String str, int off, int len) throws IOException { se.write(str, off, len); } @Override public Writer append(CharSequence csq, int start, int end) throws IOException { if (csq == null) csq = "null"; return append(csq.subSequence(start, end)); } @Override public Writer append(CharSequence csq) throws IOException { if (csq instanceof CharBuffer) { se.write((CharBuffer) csq); } else { se.write(String.valueOf(csq)); } return this; } /** * Flushes the stream. * * @exception IOException If an I/O error occurs */ public void flush() throws IOException { se.flush(); } public void close() throws IOException { se.close(); } }