THE Java™ Programming Language, Fourth Edition

public voidflush()throws IOException

Flushes the stream. If the stream has buffered any bytes from the various

write methods, flush writes them immediately to their destination. Then,

if that destination is another stream, it is also flushed. One flush invocation

will flush all the buffers in a chain of streams. If the stream is not buffered,

flush may do nothingthe default implementation. This method is defined in

the Flushable interface.

public voidclose()tHRows IOException

Closes the output stream. This method should be invoked to release any

resources (such as file descriptors) associated with the stream. Once a stream

has been closed, further operations on the stream will throw an

IOException. Closing a previously closed stream has no effect.The

default implementation of close does nothing.

The implementation of OutputStream requires only that a subclass provide the single-byte variant of
write because the other write methods are defined in terms of this one. Most streams, however, can
improve performance by overriding other methods as well. The default implementations of flush and
close will usually need to be overridden as appropriate for a particular streamin particular, buffered streams
may need to flush when closed.

Here is a program that copies its input to its output, translating one particular byte value to a different one
along the way. The TRanslateByte program takes two parameters: a from byte and a to byte. Bytes that
match the value in the string from are translated into the value in the string to.

import java.io.*;

class TranslateByte {
public static void main(String[] args)
throws IOException
{
byte from = (byte) args[0].charAt(0);
byte to = (byte) args[1].charAt(0);
int b;
while ((b = System.in.read()) != -1)
System.out.write(b == from? to : b);
}
}

For example, if we invoked the program as

java TranslateByte b B

and entered the text abracadabra!, we would get the output

aBracadaBra!