File I/O - Absolute Java - page 590

opening a file The program opens the Scanner stream and connects it to the text file morestuff.txt

as follows:

Scanner inputStream = null ;
...
inputStream = new Scanner( new FileInputStream("stuff.txt"));

The class Scanner , like the class PrintWriter , has no constructor that takes a
file name as its argument, so we need to use another class—in this case, the class
FileInputStream —to convert the file name to an object that can be a suitable
argument to the Scanner constructor.
Note that the methods nextInt and nextLine read from the text files in exactly
the same way as they read from the keyboard. The other Scanner methods for reading
input (given in Display 2.6 and repeated in Display 10.6 ) also behave the same when
reading from a text file as they do when used to read from the keyboard.

Opening a Text File for Reading with Scanner
Create a stream of the class Scanner and connect it to a text file for reading as follows:
SYNTAX
Scanner Stream_Object =
new Scanner( new FileInputStream( File_Name ));

EXAMPLE
Scanner inputStream =
new Scanner( new FileInputStream("morestuff.txt"));

After this statement, you can use the methods nextInt , nextDouble , nextLine , and so
forth to read from the named text files just as you have used these methods to read from
the keyboard.
When used in this way, the FileInputStream constructor, and hence the Scanner constructor
invocation, can throw a FileNotFoundException , which is a kind of IOException .

FileNotFoundException
If your program attempts to open a file for reading and there is no such file,
then a FileNotFoundException is thrown. As you saw earlier in this chapter,
a FileNotFoundException is also thrown in some other situations. A
FileNotFoundException is a kind of IOException .