java.io.FilterInputStream and java.io.FilterOutputStream
classes are concrete subclasses of InputStream
and OutputStream
that somehow modify data read from an underlying stream. You rarely use these classes directly, but their subclasses are extremely important, especially DataInputStream and DataOutputStream.
You connect filter streams to an underlying stream that supplies the actual bytes of data by passing the original stream to the filter stream's constructor. For example, to create a new DataOutputStream
from a FileOutputStream you might do this:
FileOutputStream fos = new FileOutputStream("ln.txt");
DataOutputStream dos = new DataOutputStream(fos);
DataOutputStream dos = new DataOutputStream(new FileOutputStream("ln.txt"));