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Class Writer

java.lang.Object
java.io.Writer
All Implemented Interfaces:
Closeable, Flushable, Appendable, AutoCloseable
Direct Known Subclasses:
BufferedWriter, CharArrayWriter, FilterWriter, OutputStreamWriter, PipedWriter, PrintWriter, StringWriter 
public abstract class Writer extends Object implements Appendable, Closeable, Flushable
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.
Since:
1.1
See Also:

Field Summary

Modifier and Type Field Description
protected Object lock
The object used to synchronize operations on this stream.

Constructor Summary

Writer()
Writer(Object lock)
Modifier Constructor Description
protected
Creates a new character-stream writer whose critical sections will synchronize on the writer itself.
protected
Creates a new character-stream writer whose critical sections will synchronize on the given object.

Method Summary

Modifier and Type Method Description
Writer append(char c)
Appends the specified character to this writer.
Writer append(CharSequence csq)
Appends the specified character sequence to this writer.
Writer append(CharSequence csq, int start, int end)
Appends a subsequence of the specified character sequence to this writer.
abstract void close()
Closes the stream, flushing it first.
abstract void flush()
Flushes the stream.
static Writer nullWriter()
Returns a new Writer which discards all characters.
void write(char[] cbuf)
Writes an array of characters.
abstract void write(char[] cbuf, int off, int len)
Writes a portion of an array of characters.
void write(int c)
Writes a single character.
void write(String str)
Writes a string.
void write(String str, int off, int len)
Writes a portion of a string.

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

lock

protected Object lock
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 this or a synchronized method.

Constructor Details

Writer

protected Writer()
Creates a new character-stream writer whose critical sections will synchronize on the writer itself.

Writer

protected Writer(Object lock)
Creates a new character-stream writer whose critical sections will synchronize on the given object.
Parameters:
lock - Object to synchronize on

Method Details

nullWriter

public static Writer nullWriter()
Returns a new Writer which discards all characters. The returned stream is initially open. The stream is closed by calling the close() method. Subsequent calls to close() have no effect.

While the stream is open, the append(char), append(CharSequence), append(CharSequence, int, int), flush(), write(int), write(char[]), and write(char[], int, int) methods do nothing. After the stream has been closed, these methods all throw IOException.

The object used to synchronize operations on the returned Writer is not specified.

Returns:
a Writer which discards all characters
Since:
11

write

public void write(int c) throws IOException
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.

Subclasses that intend to support efficient single-character output should override this method.

Parameters:
c - int specifying a character to be written
Throws:
IOException - If an I/O error occurs

write

public void write(char[] cbuf) throws IOException
Writes an array of characters.
Parameters:
cbuf - Array of characters to be written
Throws:
IOException - If an I/O error occurs

write

public abstract void write(char[] cbuf, int off, int len) throws IOException
Writes a portion of an array of characters.
Parameters:
cbuf - Array of characters
off - Offset from which to start writing characters
len - Number of characters to write
Throws:
IndexOutOfBoundsException - Implementations should throw this exception if off is negative, or len is negative, or off + len is negative or greater than the length of the given array
IOException - If an I/O error occurs

write

public void write(String str) throws IOException
Writes a string.
Parameters:
str - String to be written
Throws:
IOException - If an I/O error occurs

write

public void write(String str, int off, int len) throws IOException
Writes a portion of a string.
Implementation Requirements:
The implementation in this class throws an IndexOutOfBoundsException for the indicated conditions; overriding methods may choose to do otherwise.
Parameters:
str - A String
off - Offset from which to start writing characters
len - Number of characters to write
Throws:
IndexOutOfBoundsException - Implementations should throw this exception if off is negative, or len is negative, or off + len is negative or greater than the length of the given string
IOException - If an I/O error occurs

append

public Writer append(CharSequence csq) throws IOException
Appends the specified character sequence to this writer.

An invocation of this method of the form out.append(csq) behaves in exactly the same way as the invocation 

    out.write(csq.toString())

Depending on the specification of toString for the character sequence csq, the entire sequence may not be appended. For instance, invoking the toString method of a character buffer will return a subsequence whose content depends upon the buffer's position and limit.

Specified by:
append in interface Appendable
Parameters:
csq - The character sequence to append. If csq is null, then the four characters "null" are appended to this writer.
Returns:
This writer
Throws:
IOException - If an I/O error occurs
Since:
1.5

append

public Writer append(CharSequence csq, int start, int end) throws IOException
Appends a subsequence of the specified character sequence to this writer. Appendable.

An invocation of this method of the form out.append(csq, start, end) when csq is not null behaves in exactly the same way as the invocation 

    out.write(csq.subSequence(start, end).toString())
Specified by:
append in interface Appendable
Parameters:
csq - The character sequence from which a subsequence will be appended. If csq is null, then characters will be appended as if csq contained the four characters "null".
start - The index of the first character in the subsequence
end - The index of the character following the last character in the subsequence
Returns:
This writer
Throws:
IndexOutOfBoundsException - If start or end are negative, start is greater than end, or end is greater than csq.length()
IOException - If an I/O error occurs
Since:
1.5

append

public Writer append(char c) throws IOException
Appends the specified character to this writer.

An invocation of this method of the form out.append(c) behaves in exactly the same way as the invocation 

    out.write(c)
Specified by:
append in interface Appendable
Parameters:
c - The 16-bit character to append
Returns:
This writer
Throws:
IOException - If an I/O error occurs
Since:
1.5

flush

public abstract void flush() throws IOException
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.

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.

Specified by:
flush in interface Flushable
Throws:
IOException - If an I/O error occurs

close

public abstract void close() 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.
Specified by:
close in interface AutoCloseable
Specified by:
close in interface Closeable
Throws:
IOException - If an I/O error occurs

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/io/Writer.html