Writer

public abstract class Writer
extends Object implements Appendable, Closeable, Flushable

java.lang.Object
   ↳ java.io.Writer


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.

Summary

Fields

protected Object lock

The object used to synchronize operations on this stream.

Protected constructors

Writer()

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

Writer(Object lock)

Creates a new character-stream writer whose critical sections will synchronize on the given object.

Public methods

Writer append(char c)

Appends the specified character to this writer.

Writer append(CharSequence csq, int start, int end)

Appends a subsequence of the specified character sequence to this writer.

Writer append(CharSequence csq)

Appends 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(String str)

Writes a string.

void write(int c)

Writes a single character.

void write(String str, int off, int len)

Writes a portion of a string.

abstract void write(char[] cbuf, int off, int len)

Writes a portion of an array of characters.

void write(char[] cbuf)

Writes an array of characters.

Inherited methods

Fields

lock

Added in API level 1
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.

Protected constructors

Writer

Added in API level 1
protected Writer ()

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

Writer

Added in API level 1
protected Writer (Object lock)

Creates a new character-stream writer whose critical sections will synchronize on the given object.

Parameters
lock Object: Object to synchronize on

Public methods

append

Added in API level 1
public Writer append (char c)

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) 

Parameters
c char: The 16-bit character to append

Returns
Writer This writer

Throws
IOException If an I/O error occurs

append

Added in API level 1
public Writer append (CharSequence csq, 
                int start, 
                int end)

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())
 

Parameters
csq CharSequence: 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 int: The index of the first character in the subsequence

end int: The index of the character following the last character in the subsequence

Returns
Writer 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

append

Added in API level 1
public Writer append (CharSequence csq)

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.

Parameters
csq CharSequence: The character sequence to append. If csq is null, then the four characters "null" are appended to this writer.

Returns
Writer This writer

Throws
IOException If an I/O error occurs

close

Added in API level 1
public abstract void close ()

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

flush

Added in API level 1
public abstract void flush ()

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.

Throws
IOException If an I/O error occurs

nullWriter

Added in API level 33
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
Writer a Writer which discards all characters

write

Added in API level 1
public void write (String str)

Writes a string.

Parameters
str String: String to be written

Throws
IOException If an I/O error occurs

write

Added in API level 1
public void write (int c)

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: int specifying a character to be written

Throws
IOException If an I/O error occurs

write

Added in API level 1
public void write (String str, 
                int off, 
                int len)

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 String: A String

off int: Offset from which to start writing characters

len int: 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

write

Added in API level 1
public abstract void write (char[] cbuf, 
                int off, 
                int len)

Writes a portion of an array of characters.

Parameters
cbuf char: Array of characters

off int: Offset from which to start writing characters

len int: 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

Added in API level 1
public void write (char[] cbuf)

Writes an array of characters.

Parameters
cbuf char: Array of characters to be written

Throws
IOException If an I/O error occurs