OutputStreamWriter
/* * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.io; 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. The size of * this buffer may be specified, but by default it is large enough for most * purposes. 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 * <tt>char</tt> 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 JDK1.1 */ 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 <tt>null</tt> 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 * * @exception 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 * * @exception IOException If an I/O error occurs */ public void write(String str, int off, int len) throws IOException { se.write(str, off, len); } /** * 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(); } }
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原文地址:http://www.cnblogs.com/herd/p/16268186.html
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