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326 lines
9.3 KiB
326 lines
9.3 KiB
/*
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* Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.io;
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/**
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* Abstract class for writing to character streams. The only methods that a
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* subclass must implement are write(char[], int, int), flush(), and close().
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* Most subclasses, however, will override some of the methods defined here in
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* order to provide higher efficiency, additional functionality, or both.
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*
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* @see Writer
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* @see BufferedWriter
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* @see CharArrayWriter
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* @see FilterWriter
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* @see OutputStreamWriter
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* @see FileWriter
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* @see PipedWriter
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* @see PrintWriter
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* @see StringWriter
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* @see Reader
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*
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* @author Mark Reinhold
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* @since JDK1.1
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*/
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public abstract class Writer implements Appendable, Closeable, Flushable {
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/**
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* Temporary buffer used to hold writes of strings and single characters
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*/
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private char[] writeBuffer;
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/**
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* Size of writeBuffer, must be >= 1
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*/
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private static final int WRITE_BUFFER_SIZE = 1024;
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/**
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* The object used to synchronize operations on this stream. For
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* efficiency, a character-stream object may use an object other than
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* itself to protect critical sections. A subclass should therefore use
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* the object in this field rather than <tt>this</tt> or a synchronized
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* method.
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*/
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protected Object lock;
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/**
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* Creates a new character-stream writer whose critical sections will
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* synchronize on the writer itself.
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*/
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protected Writer() {
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this.lock = this;
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}
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/**
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* Creates a new character-stream writer whose critical sections will
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* synchronize on the given object.
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*
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* @param lock
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* Object to synchronize on
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*/
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protected Writer(Object lock) {
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if (lock == null) {
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throw new NullPointerException();
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}
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this.lock = lock;
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}
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/**
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* Writes a single character. The character to be written is contained in
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* the 16 low-order bits of the given integer value; the 16 high-order bits
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* are ignored.
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*
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* <p> Subclasses that intend to support efficient single-character output
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* should override this method.
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*
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* @param c
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* int specifying a character to be written
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*
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* @throws IOException
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* If an I/O error occurs
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*/
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public void write(int c) throws IOException {
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synchronized (lock) {
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if (writeBuffer == null){
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writeBuffer = new char[WRITE_BUFFER_SIZE];
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}
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writeBuffer[0] = (char) c;
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write(writeBuffer, 0, 1);
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}
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}
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/**
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* Writes an array of characters.
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*
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* @param cbuf
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* Array of characters to be written
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*
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* @throws IOException
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* If an I/O error occurs
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*/
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public void write(char cbuf[]) throws IOException {
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write(cbuf, 0, cbuf.length);
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}
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/**
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* Writes a portion of an array of characters.
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*
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* @param cbuf
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* Array of characters
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*
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* @param off
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* Offset from which to start writing characters
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*
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* @param len
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* Number of characters to write
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*
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* @throws IOException
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* If an I/O error occurs
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*/
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abstract public void write(char cbuf[], int off, int len) throws IOException;
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/**
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* Writes a string.
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*
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* @param str
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* String to be written
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*
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* @throws IOException
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* If an I/O error occurs
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*/
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public void write(String str) throws IOException {
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write(str, 0, str.length());
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}
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/**
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* Writes a portion of a string.
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*
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* @param str
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* A String
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*
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* @param off
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* Offset from which to start writing characters
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*
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* @param len
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* Number of characters to write
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*
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* @throws IndexOutOfBoundsException
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* If <tt>off</tt> is negative, or <tt>len</tt> is negative,
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* or <tt>off+len</tt> is negative or greater than the length
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* of the given string
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*
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* @throws IOException
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* If an I/O error occurs
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*/
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public void write(String str, int off, int len) throws IOException {
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synchronized (lock) {
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char cbuf[];
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if (len <= WRITE_BUFFER_SIZE) {
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if (writeBuffer == null) {
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writeBuffer = new char[WRITE_BUFFER_SIZE];
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}
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cbuf = writeBuffer;
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} else { // Don't permanently allocate very large buffers.
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cbuf = new char[len];
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}
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str.getChars(off, (off + len), cbuf, 0);
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write(cbuf, 0, len);
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}
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}
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/**
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* Appends the specified character sequence to this writer.
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*
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* <p> An invocation of this method of the form <tt>out.append(csq)</tt>
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* behaves in exactly the same way as the invocation
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*
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* <pre>
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* out.write(csq.toString()) </pre>
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*
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* <p> Depending on the specification of <tt>toString</tt> for the
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* character sequence <tt>csq</tt>, the entire sequence may not be
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* appended. For instance, invoking the <tt>toString</tt> method of a
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* character buffer will return a subsequence whose content depends upon
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* the buffer's position and limit.
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*
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* @param csq
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* The character sequence to append. If <tt>csq</tt> is
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* <tt>null</tt>, then the four characters <tt>"null"</tt> are
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* appended to this writer.
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*
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* @return This writer
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*
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* @throws IOException
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* If an I/O error occurs
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*
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* @since 1.5
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*/
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public Writer append(CharSequence csq) throws IOException {
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if (csq == null)
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write("null");
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else
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write(csq.toString());
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return this;
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}
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/**
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* Appends a subsequence of the specified character sequence to this writer.
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* <tt>Appendable</tt>.
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*
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* <p> An invocation of this method of the form <tt>out.append(csq, start,
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* end)</tt> when <tt>csq</tt> is not <tt>null</tt> behaves in exactly the
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* same way as the invocation
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*
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* <pre>
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* out.write(csq.subSequence(start, end).toString()) </pre>
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*
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* @param csq
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* The character sequence from which a subsequence will be
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* appended. If <tt>csq</tt> is <tt>null</tt>, then characters
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* will be appended as if <tt>csq</tt> contained the four
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* characters <tt>"null"</tt>.
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*
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* @param start
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* The index of the first character in the subsequence
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*
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* @param end
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* The index of the character following the last character in the
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* subsequence
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*
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* @return This writer
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*
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* @throws IndexOutOfBoundsException
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* If <tt>start</tt> or <tt>end</tt> are negative, <tt>start</tt>
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* is greater than <tt>end</tt>, or <tt>end</tt> is greater than
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* <tt>csq.length()</tt>
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*
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* @throws IOException
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* If an I/O error occurs
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*
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* @since 1.5
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*/
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public Writer append(CharSequence csq, int start, int end) throws IOException {
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CharSequence cs = (csq == null ? "null" : csq);
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write(cs.subSequence(start, end).toString());
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return this;
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}
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/**
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* Appends the specified character to this writer.
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*
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* <p> An invocation of this method of the form <tt>out.append(c)</tt>
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* behaves in exactly the same way as the invocation
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*
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* <pre>
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* out.write(c) </pre>
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*
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* @param c
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* The 16-bit character to append
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*
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* @return This writer
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*
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* @throws IOException
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* If an I/O error occurs
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*
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* @since 1.5
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*/
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public Writer append(char c) throws IOException {
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write(c);
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return this;
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}
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/**
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* Flushes the stream. If the stream has saved any characters from the
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* various write() methods in a buffer, write them immediately to their
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* intended destination. Then, if that destination is another character or
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* byte stream, flush it. Thus one flush() invocation will flush all the
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* buffers in a chain of Writers and OutputStreams.
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*
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* <p> If the intended destination of this stream is an abstraction provided
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* by the underlying operating system, for example a file, then flushing the
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* stream guarantees only that bytes previously written to the stream are
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* passed to the operating system for writing; it does not guarantee that
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* they are actually written to a physical device such as a disk drive.
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*
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* @throws IOException
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* If an I/O error occurs
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*/
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abstract public void flush() throws IOException;
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/**
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* Closes the stream, flushing it first. Once the stream has been closed,
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* further write() or flush() invocations will cause an IOException to be
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* thrown. Closing a previously closed stream has no effect.
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*
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* @throws IOException
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* If an I/O error occurs
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*/
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abstract public void close() throws IOException;
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}
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