|
To reduce this kind of overhead, the Java platform implements buffered I/O streams. Buffered input streams read data from a memory area known as a buffer; the native input API is called only when the buffer is empty. Similarly, buffered output streams write data to a buffer, and the native output API is called only when the buffer is full.
A program can convert an unbuffered stream into a buffered stream using
the wrapping idiom we've used several times now, where the unbuffered
stream object is passed to the constructor for a buffered stream
class. Here's how you might modify the constructor invocations in the
CopyCharacters example to use buffered I/O:
inputStream =
new BufferedReader(new FileReader("xanadu.txt"));
outputStream =
new BufferedWriter(new FileWriter("characteroutput.txt"));
BufferedInputStream
and
BufferedOutputStream
create buffered byte streams, while
BufferedReader
and
BufferedWriter
create buffered character streams.
Some buffered output classes support autoflush, specified by an
optional constructor argument. When autoflush is enabled, certain key events
cause the buffer to be flushed. For example, an autoflush
PrintWriter object flushes the buffer on every
invocation of println or format. See
Formatting for more on these methods.
To flush a stream manually, invoke its flush method. The
flush method is valid on any output stream, but has no
effect unless the stream is buffered.
|
