/*
* Copyright 1996-2005 Sun Microsystems, Inc. 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. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package java.io;
/**
* Abstract class for writing to character streams. The only methods that a
* subclass must implement are write(char[], int, int), flush(), and close().
* Most subclasses, however, will override some of the methods defined here in
* order to provide higher efficiency, additional functionality, or both.
*
* @see Writer
* @see BufferedWriter
* @see CharArrayWriter
* @see FilterWriter
* @see OutputStreamWriter
* @see FileWriter
* @see PipedWriter
* @see PrintWriter
* @see StringWriter
* @see Reader
*
* @version 1.35, 07/05/05
* @author Mark Reinhold
* @since JDK1.1
*/
public abstract class Writer implements Appendable, Closeable,
Flushable {
/**
* Temporary buffer used to hold writes of strings and single characters
*/
private char[] writeBuffer;
/**
* Size of writeBuffer, must be >= 1
*/
private final int writeBufferSize = 1024;
/**
* The object used to synchronize operations on this stream. For
* efficiency, a character-stream object may use an object other than
* itself to protect critical sections. A subclass should therefore use
* the object in this field rather than <tt>this</tt> or a synchronized
* method.
*/
protected Object lock;
/**
* Creates a new character-stream writer whose critical sections will
* synchronize on the writer itself.
*/
protected Writer() {
this .lock = this ;
}
/**
* Creates a new character-stream writer whose critical sections will
* synchronize on the given object.
*
* @param lock
* Object to synchronize on
*/
protected Writer(Object lock) {
if (lock == null) {
throw new NullPointerException();
}
this .lock = lock;
}
/**
* Writes a single character. The character to be written is contained in
* the 16 low-order bits of the given integer value; the 16 high-order bits
* are ignored.
*
* <p> Subclasses that intend to support efficient single-character output
* should override this method.
*
* @param c
* int specifying a character to be written
*
* @throws IOException
* If an I/O error occurs
*/
public void write(int c) throws IOException {
synchronized (lock) {
if (writeBuffer == null) {
writeBuffer = new char[writeBufferSize];
}
writeBuffer[0] = (char) c;
write(writeBuffer, 0, 1);
}
}
/**
* Writes an array of characters.
*
* @param cbuf
* Array of characters to be written
*
* @throws IOException
* If an I/O error occurs
*/
public void write(char cbuf[]) throws IOException {
write(cbuf, 0, cbuf.length);
}
/**
* Writes a portion of an array of characters.
*
* @param cbuf
* Array of characters
*
* @param off
* Offset from which to start writing characters
*
* @param len
* Number of characters to write
*
* @throws IOException
* If an I/O error occurs
*/
abstract public void write(char cbuf[], int off, int len)
throws IOException;
/**
* Writes a string.
*
* @param str
* String to be written
*
* @throws IOException
* If an I/O error occurs
*/
public void write(String str) throws IOException {
write(str, 0, str.length());
}
/**
* 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 <tt>off</tt> is negative, or <tt>len</tt> is negative,
* or <tt>off+len</tt> 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 {
synchronized (lock) {
char cbuf[];
if (len <= writeBufferSize) {
if (writeBuffer == null) {
writeBuffer = new char[writeBufferSize];
}
cbuf = writeBuffer;
} else { // Don't permanently allocate very large buffers.
cbuf = new char[len];
}
str.getChars(off, (off + len), cbuf, 0);
write(cbuf, 0, len);
}
}
/**
* Appends the specified character sequence to this writer.
*
* <p> An invocation of this method of the form <tt>out.append(csq)</tt>
* behaves in exactly the same way as the invocation
*
* <pre>
* out.write(csq.toString()) </pre>
*
* <p> Depending on the specification of <tt>toString</tt> for the
* character sequence <tt>csq</tt>, the entire sequence may not be
* appended. For instance, invoking the <tt>toString</tt> method of a
* character buffer will return a subsequence whose content depends upon
* the buffer's position and limit.
*
* @param csq
* The character sequence to append. If <tt>csq</tt> is
* <tt>null</tt>, then the four characters <tt>"null"</tt> are
* appended to this writer.
*
* @return This writer
*
* @throws IOException
* If an I/O error occurs
*
* @since 1.5
*/
public Writer append(CharSequence csq) throws IOException {
if (csq == null)
write("null");
else
write(csq.toString());
return this ;
}
/**
* Appends a subsequence of the specified character sequence to this writer.
* <tt>Appendable</tt>.
*
* <p> An invocation of this method of the form <tt>out.append(csq, start,
* end)</tt> when <tt>csq</tt> is not <tt>null</tt> behaves in exactly the
* same way as the invocation
*
* <pre>
* out.write(csq.subSequence(start, end).toString()) </pre>
*
* @param csq
* The character sequence from which a subsequence will be
* appended. If <tt>csq</tt> is <tt>null</tt>, then characters
* will be appended as if <tt>csq</tt> contained the four
* characters <tt>"null"</tt>.
*
* @param start
* The index of the first character in the subsequence
*
* @param end
* The index of the character following the last character in the
* subsequence
*
* @return This writer
*
* @throws IndexOutOfBoundsException
* If <tt>start</tt> or <tt>end</tt> are negative, <tt>start</tt>
* is greater than <tt>end</tt>, or <tt>end</tt> is greater than
* <tt>csq.length()</tt>
*
* @throws IOException
* If an I/O error occurs
*
* @since 1.5
*/
public Writer append(CharSequence csq, int start, int end)
throws IOException {
CharSequence cs = (csq == null ? "null" : csq);
write(cs.subSequence(start, end).toString());
return this ;
}
/**
* Appends the specified character to this writer.
*
* <p> An invocation of this method of the form <tt>out.append(c)</tt>
* behaves in exactly the same way as the invocation
*
* <pre>
* out.write(c) </pre>
*
* @param c
* The 16-bit character to append
*
* @return This writer
*
* @throws IOException
* If an I/O error occurs
*
* @since 1.5
*/
public Writer append(char c) throws IOException {
write(c);
return this ;
}
/**
* Flushes the stream. If the stream has saved any characters from the
* various write() methods in a buffer, write them immediately to their
* intended destination. Then, if that destination is another character or
* byte stream, flush it. Thus one flush() invocation will flush all the
* buffers in a chain of Writers and OutputStreams.
*
* <p> If the intended destination of this stream is an abstraction provided
* by the underlying operating system, for example a file, then flushing the
* stream guarantees only that bytes previously written to the stream are
* passed to the operating system for writing; it does not guarantee that
* they are actually written to a physical device such as a disk drive.
*
* @throws IOException
* If an I/O error occurs
*/
abstract public void flush() throws IOException;
/**
* Closes the stream, flushing it first. Once the stream has been closed,
* further write() or flush() invocations will cause an IOException to be
* thrown. Closing a previously closed stream has no effect.
*
* @throws IOException
* If an I/O error occurs
*/
abstract public void close() throws IOException;
}
|
