FileDocCategorySizeDatePackage
Writer.javaAPI DocJ2ME CLDC 1.15081Wed Feb 05 15:55:58 GMT 2003java.io

Writer

public abstract class Writer extends Object
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.
version
12/17/01 (CLDC 1.1)
author
Mark Reinhold
since
JDK1.1, CLDC 1.0
see
java.io.OutputStreamWriter
see
java.io.Reader

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


                       
      
        this.lock = this;
    
protected Writer(Object lock)
Create 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 abstract voidclose()
Close the stream, flushing it first. Once a stream has been closed, further write() or flush() invocations will cause an IOException to be thrown. Closing a previously-closed stream, however, has no effect.

exception
IOException If an I/O error occurs

public abstract voidflush()
Flush 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.

exception
IOException If an I/O error occurs

public voidwrite(int c)
Write 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.
exception
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)
Write an array of characters.

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

        write(cbuf, 0, cbuf.length);
    
public abstract voidwrite(char[] cbuf, int off, int len)
Write 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
exception
IOException If an I/O error occurs

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

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

        write(str, 0, str.length());
    
public voidwrite(java.lang.String str, int off, int len)
Write 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
exception
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);
        }