Input/Output - Beginning Java 8 Language Features - page 337

Table 7-5. Comparing Classes from Byte-based Output Streams and Character-based Output Streams

Byte-based Output Stream Class Character-based Output Stream Class

OutputStream Writer

ByteArrayOutputStream CharArrayWriter

StringWriter No corresponding class

PipedOutputStream PipedWriter

FileOutputStream FileWriter

OutputStreamWriter No corresponding class

FilterOutputStream FilterWriter

BufferedOutputStream BufferedWriter

DataOutputStream

No corresponding class

ObjectOutputStream No corresponding class

PrintStream PrintWriter

Some of the classes in the byte-based input/output streams do not have the corresponding character-based
classes and vice versa. For example, reading and writing primitive data and objects are always byte-based; therefore,
you do not have any classes in the reader/writer class family corresponding to the data/object input/output streams.
I have discussed how to use the byte-based input/output classes in detail in the previous sections. You will find
the classes in the reader/writer and the input/output categories similar. They are also based on the decorator pattern.
In the reader class hierarchy, BufferedReader , which is a concrete decorator, is directly inherited from the Reader
class instead of the abstract decorator FilterReader class. In the writer class hierarchy, all concrete decorators have been
inherited from the Writer class instead of the FilterWriter . No concrete decorator inherits the FilterWriter class.
The two classes, InputStreamReader and OutputStreamWriter , in the reader/writer class family provide the
bridge between the byte-based and character-based streams. If you have an instance of InputStream and you
want to get a Reader from it, you can get that by using the InputStreamReader class. That is, you need to use the
InputStreamReader class if you have a stream that supplies bytes and you want to read characters by getting those
bytes decoded into characters for you. For example, if you have an InputStream object called iso , and you want to get
a Reader object instance, you can do so as follows:

// Create a Reader object from an InputStream object using the
// platform default encoding
Reader reader = new InputStreamReader(iso);

If you know the encoding used in the byte-based stream, you can specify it while creating a Reader object as follows:

// Create a Reader object from an InputStream using the "US-ASCII" encoding
Reader reader = new InputStreamReader(iso, "US-ASCII");

Similarly, you can create a Writer object to spit out characters from a bytes-based output stream as follows,
assuming that oso is an OutputStream object:

// Create a Writer object from OutputStream using the platform default encoding
Writer writer = new OutputStreamWriter(oso);