Standard Streams in java

Standard Streams are a feature provided by many operating systems. By default, they read input from the keyboard and write output to the display. They also support I/O operations on files.

Java also supports three Standard Streams:

• Standard Input: Accessed through System.in which is used to read input from the keyboard.
• Standard Output: Accessed through System.out which is used to write output to be display.
• Standard Error: Accessed through System.err which is used to write error output to be display.

These objects are defined automatically and do not need to be opened explicitly. Standard Output and Standard Error, both are to write output; having error output separately so that the user may read error messages efficiently.
System.in is a byte stream that has no character stream features. To use Standard Input as a character stream, wrap System.in within the InputStreamReader as an argument.

InputStreamReader inp = new InputStreamReader(system.in);