Scanner has been used with the standard input stream:
Scanner scan = new Scanner( System.in );
The previous chapter showed how to use input redirection to connect System.in to a disk file.
Recall, from chapter 12, that input and output are done with streams of data. There is a standard input stream, a standard output stream, and a standard error stream.
A Scanner object constructed with System.in
scans the standard input stream for groups of characters.
The groups can be characters separated by spaces
or complete lines of text.
A group of characters separated by spaces is called a token. By default, tokens are surrounded (delimited) by spaces, tabs, or the beginning and ends of lines.
Some Scanner methods convert a token into a specific data type.
For example,
the nextInt() method reads in a group of characters that
can be converted to an int.
Could the characters of an input stream come from a disk file?