Module java.base

Package java.io

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:

• BufferedWriter
• CharArrayWriter
• FilterWriter
• OutputStreamWriter
• FileWriter
• PipedWriter
• PrintWriter
• StringWriter
• Reader

Field Summary

Fields

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

Constructor Summary

Constructors

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