Handling Input and Output - Beginning Java Programming: The Object-Oriented Approach - page 276

Writer out = new FileWriter("groceries (copy).txt");
) {
int c;
while ((c = in.read()) != -1) {
out.write(c);
System.out.print((char) c);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}

3.

Execute the program. You'll see that it behaves similarly as before.

How It Works
Here's how it works:
1.

We're now using the FileReader and FileWriter classes here to open the original file as a data
source and a new file as a destination. If the file does not exist, the program will attempt to create
it. If the file does exist, its contents are overridden, unless you pass true as the second argument of
the FileWriter constructor.

2.

The rest of the program is performed very similarly to using byte streams. Note that we're using
a try-with-resources block to handle the closing of the Reader and the Writer automatically. If
you use a traditional try-catch block, do not forget to add a finally clause when you close the
Reader and Writer .

3.

With our Reader and Writer acting so similarly to our InputStream and OutputStream , you
might be wondering why it makes sense to use character streams in the first place. The first differ-
ence lies in the fact that Reader s and Writer s store characters in the last 16 bits of an int , and
thus support a wider range of characters. Byte streams read and write bytes, that is, they store a
byte in the last eight bits of an int . For this simple English grocery list, the difference is not notice-
able, but once you start adding a wider range of characters, you'll see that character streams are
the right route to follow. Second, when dealing with text files, you might often be interested in
working with bigger units than just a single byte (or character), for example to read and show
lines. With Reader s and Writer s, you can do so, although you first need to add another stream
type to the mix, as you'll see in the following section on buffered streams.

Next, note the existance of InputStreamReader and OutputStreamReader to create byte-to-char-
acter bridges when no native character stream class exists to meet your data source/destination (you
will see a situation later on where this becomes useful). The PrintWriter class, finally, is the char-
acter stream counterpart of the PrintStream class.

Buffered streams
Most streams in Java are unbuffered, meaning that each write and read request is handled directly
by the operating system. This makes programs less efficient, as every write request to a file, for
instance, will trigger disk access or some other time-consuming operation. Therefore, buffered