bufferedwriter.java

This is a resource based on j2me embedded,if you dont understand,you can connection with me .

/*
 * @(#)BufferedWriter.java	1.29 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program 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.   
 *   
 * This program 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 at /legal/license.txt).   
 *   
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.io;


/**
 * Write text to a character-output stream, buffering characters so as to
 * provide for the efficient writing of single characters, arrays, and strings.
 *
 * <p> The buffer size may be specified, or the default size may be accepted.
 * The default is large enough for most purposes.
 *
 * <p> A newLine() method is provided, which uses the platform's own notion of
 * line separator as defined by the system property <tt>line.separator</tt>.
 * Not all platforms use the newline character ('\n') to terminate lines.
 * Calling this method to terminate each output line is therefore preferred to
 * writing a newline character directly.
 *
 * <p> In general, a Writer sends its output immediately to the underlying
 * character or byte stream.  Unless prompt output is required, it is advisable
 * to wrap a BufferedWriter around any Writer whose write() operations may be
 * costly, such as FileWriters and OutputStreamWriters.  For example,
 *
 * <pre>
 * PrintWriter out
 *   = new PrintWriter(new BufferedWriter(new FileWriter("foo.out")));
 * </pre>
 *
 * will buffer the PrintWriter's output to the file.  Without buffering, each
 * invocation of a print() method would cause characters to be converted into
 * bytes that would then be written immediately to the file, which can be very
 * inefficient.
 *
 * @see PrintWriter
 * @see FileWriter
 * @see OutputStreamWriter
 *
 * @version 	1.22, 00/02/02
 * @author	Mark Reinhold
 * @since	JDK1.1
 */

public class BufferedWriter extends Writer {

    private Writer out;

    private char cb[];
    private int nChars, nextChar;

    private static int defaultCharBufferSize = 8192;

    /**
     * Line separator string.  This is the value of the line.separator
     * property at the moment that the stream was created.
     */
    private String lineSeparator;

    /**
     * Create a buffered character-output stream that uses a default-sized
     * output buffer.
     *
     * @param  out  A Writer
     */
    public BufferedWriter(Writer out) {
	this(out, defaultCharBufferSize);
    }

    /**
     * Create a new buffered character-output stream that uses an output
     * buffer of the given size.
     *
     * @param  out  A Writer
     * @param  sz   Output-buffer size, a positive integer
     *
     * @exception  IllegalArgumentException  If sz is <= 0
     */
    public BufferedWriter(Writer out, int sz) {
	super(out);
	if (sz <= 0)
	    throw new IllegalArgumentException("Buffer size <= 0");
	this.out = out;
	cb = new char[sz];
	nChars = sz;
	nextChar = 0;

	lineSeparator =	(String) java.security.AccessController.doPrivileged(
               new sun.security.action.GetPropertyAction("line.separator"));
    }

    /** Check to make sure that the stream has not been closed */
    private void ensureOpen() throws IOException {
	if (out == null)
	    throw new IOException("Stream closed");
    }

    /**
     * Flush the output buffer to the underlying character stream, without
     * flushing the stream itself.  This method is non-private only so that it
     * may be invoked by PrintStream.
     */
    void flushBuffer() throws IOException {
	synchronized (lock) {
	    ensureOpen();
	    if (nextChar == 0)
		return;
	    out.write(cb, 0, nextChar);
	    nextChar = 0;
	}
    }

    /**
     * Write a single character.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void write(int c) throws IOException {
	synchronized (lock) {
	    ensureOpen();
	    if (nextChar >= nChars)
		flushBuffer();
	    cb[nextChar++] = (char) c;
	}
    }

    /**
     * Our own little min method, to avoid loading java.lang.Math if we've run
     * out of file descriptors and we're trying to print a stack trace.
     */
    private int min(int a, int b) {
	if (a < b) return a;
	return b;
    }

    /**
     * Write a portion of an array of characters.
     *
     * <p> Ordinarily this method stores characters from the given array into
     * this stream's buffer, flushing the buffer to the underlying stream as
     * needed.  If the requested length is at least as large as the buffer,
     * however, then this method will flush the buffer and write the characters
     * directly to the underlying stream.  Thus redundant
     * <code>BufferedWriter</code>s will not copy data unnecessarily.
     *
     * @param  cbuf  A character array
     * @param  off   Offset from which to start reading 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 {
	synchronized (lock) {
	    ensureOpen();
            if ((off < 0) || (off > cbuf.length) || (len < 0) ||
                ((off + len) > cbuf.length) || ((off + len) < 0)) {
                throw new IndexOutOfBoundsException();
            } else if (len == 0) {
                return;
            } 

	    if (len >= nChars) {
		/* If the request length exceeds the size of the output buffer,
		   flush the buffer and then write the data directly.  In this
		   way buffered streams will cascade harmlessly. */
		flushBuffer();
		out.write(cbuf, off, len);
		return;
	    }

	    int b = off, t = off + len;
	    while (b < t) {
		int d = min(nChars - nextChar, t - b);
		System.arraycopy(cbuf, b, cb, nextChar, d);
		b += d;
		nextChar += d;
		if (nextChar >= nChars)
		    flushBuffer();
	    }
	}
    }

    /**
     * Write a portion of a String.
     *
     * @param  s     String to be written
     * @param  off   Offset from which to start reading characters
     * @param  len   Number of characters to be written
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void write(String s, int off, int len) throws IOException {
	synchronized (lock) {
	    ensureOpen();

	    int b = off, t = off + len;
	    while (b < t) {
		int d = min(nChars - nextChar, t - b);
		s.getChars(b, b + d, cb, nextChar);
		b += d;
		nextChar += d;
		if (nextChar >= nChars)
		    flushBuffer();
	    }
	}
    }

    /**
     * Write a line separator.  The line separator string is defined by the
     * system property <tt>line.separator</tt>, and is not necessarily a single
     * newline ('\n') character.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void newLine() throws IOException {
	write(lineSeparator);
    }

    /**
     * Flush the stream.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void flush() throws IOException {
	synchronized (lock) {
	    flushBuffer();
	    out.flush();
	}
    }

    /**
     * Close the stream.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void close() throws IOException {
	synchronized (lock) {
	    if (out == null)
		return;
	    flushBuffer();
	    out.close();
	    out = null;
	    cb = null;
	}
    }

}