7.2 The InputStream class

The InputStream class is an abstract class from which all input streams inherit. It has several methods that are common to all input streams. These methods are:

available	Returns the number of bytes that can be read from this input stream without blocking.
close	Closes this input stream and releases any system resources associated with the stream.
mark	Marks the current position in this input stream. This position can be returned to by calling reset.
markSupported	Returns true if this input stream supports the mark and reset methods.
read	Reads the next byte of data from this input stream. This method is overloaded so that an array of bytes can also be read.
reset	Repositions this stream to the position at the time the mark method was last called on this input stream.
skip	Skips over and discards n bytes of data from this input stream.

Some of the sub-classes of InputStream are:

ByteArrayInputStream - This stream allows an array of bytes to be treated as a stream.
DataInputStream - This stream allows an application to read primitive Java data types from a stream.
FileInputStream - This stream reads from a file.
BufferedInputStream - This stream buffers the reading of another input stream. This improves can improve the performance of reading from a stream.

Source

Java API documentation