The job of a computer is to take an input and give an output, to us input is a feed that translated in a machine language and then displayed back as a readable format. Further

All Java data is written and read using streams.
At the time of preparing this manuscript, Sun Micro conveyed the following items to deal with input-output of texts or objects.
  • I/O Streams
  • Byte Streams: carries integer values of the data added as an input. (1), ranging a value 0-255 and 32 being a blank or space between two data during serialization. All byte stream classes are the descendents of  InputStream and OutputStream (Read More). Java uses byte streams to perform input and output of 8-bit bytes. These classes are abstract classes, therefore can't be stream directly.
    • FileInputStream in = null;
    • FileOutputStream out = null;
      •  I/O byte streams, FileInputStream and FileOutputStream.
  • Character Streams: Any kind of text data handled by this stream. All character stream classes are descended from Reader and Writer.(Read More)
    • FileReader inputStream = null;
    • FileWriter outputStream = null;
  • Buffered Streams: the efficiency of the streams mentioned above, further  enhanced with Buffered stream.
    • There are four buffered stream classes used to wrap FileReader or Writer streams:
      •  Create buffered byte streams:
        • BufferedInputStream and BufferedOutputStream
      • Create buffered character streams
        •  BufferedReader and BufferedWriter.
  • Scanning and Formatting
    • Scanning:
      • Scanner
        • BufferedReader(new FileReader("xanadu.txt")));
    • Formatting
  • I/O from the Command Line
  • Data Streams: support binary I/O of primitive data type values like boolean, char, byte, short, int, long, float, double and Strings. All data streams implement either the two interfaces namely DataInput  or the DataOutput interface. This section focuses on the most widely-used implementations of these interfaces, DataInputStream and DataOutputStream.
  • Object Stream
    • ObjectOutputStream(OOPS) Link
  • File I/Omakes it easier to write platform-independent code that examines and manipulates files. The name of this class is misleading: File instances represent file names, not files. The file corresponding to the file name might not even exist.
    File Objects
    Random Access Files
    The New I/O Packages
 
An InputStreamReader is a bridge from byte streams to character streams: It reads bytes and translates them into characters according to a specified character encoding. The encoding that it uses may be specified by name, or the platform's default encoding may be accepted.

Each invocation of one of an InputStreamReader's read() methods may cause one or more bytes to be read from the underlying byte-input stream. To enable the efficient conversion of bytes to characters, more bytes may be read ahead from the underlying stream than are necessary to satisfy the current read operation.

For top efficiency, consider wrapping an InputStreamReader within a BufferedReader. For example: 

 BufferedReader in
   = new BufferedReader(new InputStreamReader(System.in));