Input/Output - Beginning Java 8 Language Features - page 313

Table 7-3. Comparing Classes in the Decorator Pattern, the Drink Application, and the Output Streams

Decorator Pattern Drink Application Output Stream

Component Drink OutputStream

ConcreteComponentA
ConcreteComponentB

Rum
Vodka
Whisky

FileOutputStream
ByteArrayOutputStream
PipedOutputStream

Decorator DrinkDecorator FilterOutputStream

ConcreteDecoratorA
ConcreteDecoratorB

Honey
Spices

BufferedOutputStream
DataOutputStream
ObjectOutputStream

There are three important methods defined in the abstract superclass OutputStream : write() , flush() , and
close() . The write() method is used to write bytes to an output stream. It has three versions that let you write one
byte or multiple bytes at a time. You used it to write data to a file in the SimpleFileWriting class in Listing 7-16. The
flush() method is used to flush any buffered bytes to the data sink. The close() method closes the output stream.
The technique to use concrete decorators with the concrete component classes for the output stream is the same
as for the input stream classes. For example, to use the BufferedOutputStream decorator for better speed to write to a
file, use the following statement:

BufferedOutputStream bos = new BufferedOutputStream(
new FileOutputStream("your output file path")
);

To write data to a ByteArrayOutputStream , use

ByteArrayOutputStream baos = new ByteArrayOutputStream();
baos.write(buffer); // buffer is a byte array

ByteArrayOutputStream provides some important methods: reset() , size() , toString() , and writeTo() .
The reset() method discards all bytes written to it; the size() method returns the number of bytes written to
the stream; the toString() method returns the string representation of the bytes in the stream; the writeTo()
method writes the bytes in the stream to another output stream. For example, if you have written some bytes to a
ByteArrayOutputStream called baos and want to write its content to a file represented by FileOutputStream named
fos , you would use the following statement:

// All bytes written to baos is written to fos
baos.writeTo(fos);

I will not discuss any more examples of writing to an output stream in this section. You can use
SimpleFileWriting class in Listing 7-16 as an example to use any other output stream. You can use any output
stream's concrete decorators by using them as an enclosing object for a concrete component or another concrete
decorator. I will discuss DataOutputStream , ObjectOutputStream , and PrintStream classes with examples in
subsequent sections.