FileDocCategorySizeDatePackage
Writer.javaAPI DocJava SE 6 API9144Tue Jun 10 00:25:34 BST 2008java.io

Writer

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.
see
Writer
see
BufferedWriter
see
CharArrayWriter
see
FilterWriter
see
OutputStreamWriter
see
FileWriter
see
PipedWriter
see
PrintWriter
see
StringWriter
see
Reader
version
1.29, 05/11/17
author
Mark Reinhold
since
JDK1.1

Fields Summary
private char[]
writeBuffer
Temporary buffer used to hold writes of strings and single characters
private final int
writeBufferSize
Size of writeBuffer, must be >= 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.
Constructors Summary
protected Writer()
Creates a new character-stream writer whose critical sections will synchronize on the writer itself.


                       
      
	this.lock = this;
    
protected Writer(Object lock)
Creates a new character-stream writer whose critical sections will synchronize on the given object.

param
lock Object to synchronize on

	if (lock == null) {
	    throw new NullPointerException();
	}
	this.lock = lock;
    
Methods Summary
public java.io.Writerappend(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) 

param
c The 16-bit character to append
return
This writer
throws
IOException If an I/O error occurs
since
1.5

	write(c);
	return this;
    
public java.io.Writerappend(java.lang.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.

param
csq The character sequence to append. If csq is null, then the four characters "null" are appended to this writer.
return
This writer
throws
IOException If an I/O error occurs
since
1.5

	if (csq == null)
	    write("null");
	else
	    write(csq.toString());
    	return this;
    
public java.io.Writerappend(java.lang.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()) 

param
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".
param
start The index of the first character in the subsequence
param
end The index of the character following the last character in the subsequence
return
This writer
throws
IndexOutOfBoundsException If start or end are negative, start is greater than end, or end is greater than csq.length()
throws
IOException If an I/O error occurs
since
1.5

	CharSequence cs = (csq == null ? "null" : csq);
	write(cs.subSequence(start, end).toString());
 	return this; 
    
public abstract voidclose()
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

public abstract voidflush()
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

public voidwrite(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.

param
c int specifying a character to be written
throws
IOException If an I/O error occurs

	synchronized (lock) {
	    if (writeBuffer == null){
		writeBuffer = new char[writeBufferSize];
	    }
	    writeBuffer[0] = (char) c;
	    write(writeBuffer, 0, 1);
	}
    
public voidwrite(char[] cbuf)
Writes an array of characters.

param
cbuf Array of characters to be written
throws
IOException If an I/O error occurs

	write(cbuf, 0, cbuf.length);
    
public abstract voidwrite(char[] cbuf, int off, int len)
Writes a portion of an array of characters.

param
cbuf Array of characters
param
off Offset from which to start writing characters
param
len Number of characters to write
throws
IOException If an I/O error occurs

public voidwrite(java.lang.String str)
Writes a string.

param
str String to be written
throws
IOException If an I/O error occurs

	write(str, 0, str.length());
    
public voidwrite(java.lang.String str, int off, int len)
Writes a portion of a string.

param
str A String
param
off Offset from which to start writing characters
param
len Number of characters to write
throws
IndexOutOfBoundsException If off is negative, or len is negative, or off+len is negative or greater than the length of the given string
throws
IOException If an I/O error occurs

	synchronized (lock) {
	    char cbuf[];
	    if (len <= writeBufferSize) {
		if (writeBuffer == null) {
		    writeBuffer = new char[writeBufferSize];
		}
		cbuf = writeBuffer;
	    } else {	// Don't permanently allocate very large buffers.
		cbuf = new char[len];
	    }
	    str.getChars(off, (off + len), cbuf, 0);
	    write(cbuf, 0, len);
	}