/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package java.io;
/*** The base class for all writers. A writer is a means of writing data to a target in a character-wise manner. Most output streams
* expect the {@link #flush()} method to be called before closing the stream, to ensure all data is actually written out.
* <p>
* This abstract class does not provide a fully working implementation, so it needs to be subclassed, and at least the
* {@link #write(char[], int, int)}, {@link #close()} and {@link #flush()} methods needs to be overridden. Overriding some of the
* non-abstract methods is also often advised, since it might result in higher efficiency.
* <p>
* Many specialized readers for purposes like reading from a file already exist in this package.
*
* @see Reader */
public abstract class Writer implements Appendable, Closeable, Flushable {
static final String TOKEN_NULL = "null"; //$NON-NLS-1$
/*** The object used to synchronize access to the writer. */
protected Object lock;
/*** Constructs a new {@code Writer} with {@code this} as the object used to synchronize critical sections. */
protected Writer () {
super();
lock = this;
}
/*** Constructs a new {@code Writer} with {@code lock} used to synchronize critical sections.
*
* @param lock the {@code Object} used to synchronize critical sections.
* @throws NullPointerException if {@code lock} is {@code null}. */
protected Writer (Object lock) {
if (lock == null) {
throw new NullPointerException();
}
this.lock = lock;
}
/*** Closes this writer. Implementations of this method should free any resources associated with the writer.
*
* @throws IOException if an error occurs while closing this writer. */
public abstract void close () throws IOException;
/*** Flushes this writer. Implementations of this method should ensure that all buffered characters are written to the target.
*
* @throws IOException if an error occurs while flushing this writer. */
public abstract void flush () throws IOException;
/*** Writes the entire character buffer {@code buf} to the target.
*
* @param buf the non-null array containing characters to write.
* @throws IOException if this writer is closed or another I/O error occurs. */
public void write (char buf[]) throws IOException {
write(buf, 0, buf.length);
}
/*** Writes {@code count} characters starting at {@code offset} in {@code buf} to the target.
*
* @param buf the non-null character array to write.
* @param offset the index of the first character in {@code buf} to write.
* @param count the maximum number of characters to write.
* @throws IndexOutOfBoundsException if {@code offset < 0} or {@code count < 0}, or if {@code offset + count} is greater than
* the size of {@code buf}.
* @throws IOException if this writer is closed or another I/O error occurs. */
public abstract void write (char buf[], int offset, int count) throws IOException;
/*** Writes one character to the target. Only the two least significant bytes of the integer {@code oneChar} are written.
*
* @param oneChar the character to write to the target.
* @throws IOException if this writer is closed or another I/O error occurs. */
public void write (int oneChar) throws IOException {
synchronized (lock) {
char oneCharArray[] = new char[1];
oneCharArray[0] = (char)oneChar;
write(oneCharArray);
}
}
/*** Writes the characters from the specified string to the target.
*
* @param str the non-null string containing the characters to write.
* @throws IOException if this writer is closed or another I/O error occurs. */
public void write (String str) throws IOException {
write(str, 0, str.length());
}
/*** Writes {@code count} characters from {@code str} starting at {@code offset} to the target.
*
* @param str the non-null string containing the characters to write.
* @param offset the index of the first character in {@code str} to write.
* @param count the number of characters from {@code str} to write.
* @throws IOException if this writer is closed or another I/O error occurs.
* @throws IndexOutOfBoundsException if {@code offset < 0} or {@code count < 0}, or if {@code offset + count} is greater than
* the length of {@code str}. */
public void write (String str, int offset, int count) throws IOException {
if (count < 0) { // other cases tested by getChars()
throw new StringIndexOutOfBoundsException();
}
char buf[] = new char[count];
str.getChars(offset, offset + count, buf, 0);
synchronized (lock) {
write(buf, 0, buf.length);
}
}
/*** Appends the character {@code c} to the target. This method works the same way as {@link #write(int)}.
*
* @param c the character to append to the target stream.
* @return this writer.
* @throws IOException if this writer is closed or another I/O error occurs. */
public Writer append (char c) throws IOException {
write(c);
return this;
}
/*** Appends the character sequence {@code csq} to the target. This method works the same way as
* {@code Writer.write(csq.toString())}. If {@code csq} is {@code null}, then the string "null" is written to the target
* stream.
*
* @param csq the character sequence appended to the target.
* @return this writer.
* @throws IOException if this writer is closed or another I/O error occurs. */
public Writer append (CharSequence csq) throws IOException {
if (null == csq) {
write(TOKEN_NULL);
} else {
write(csq.toString());
}
return this;
}
/*** Appends a subsequence of the character sequence {@code csq} to the target. This method works the same way as
* {@code Writer.writer(csq.subsequence(start, end).toString())}. If {@code csq} is {@code null}, then the specified
* subsequence of the string "null" will be written to the target.
*
* @param csq the character sequence appended to the target.
* @param start the index of the first char in the character sequence appended to the target.
* @param end the index of the character following the last character of the subsequence appended to the target.
* @return this writer.
* @throws IOException if this writer is closed or another I/O error occurs.
* @throws IndexOutOfBoundsException if {@code start > end}, {@code start < 0}, {@code end < 0} or either {@code start} or
* {@code end} are greater or equal than the length of {@code csq}. */
public Writer append (CharSequence csq, int start, int end) throws IOException {
if (null == csq) {
write(TOKEN_NULL.substring(start, end));
} else {
write(csq.subSequence(start, end).toString());
}
return this;
}
/*** Returns true if this writer has encountered and suppressed an error. Used by PrintWriters as an alternative to checked
* exceptions. */
boolean checkError () {
return false;
}
}