File I/O - Java - page 537

Display 10.3 Reading Input from a Text File Using Scanner (part 2 of 2)
S CREEN O UTPUT
I will read three numbers and a line
of text from the file morestuff.txt.
The three numbers read from the file are:
1, 2, and 3
The line read from the file is:
Eat my shorts.
Testing for the End of a Text File with Scanner
When using the class Scanner , if your program tries to read beyond the end of the file
with any of the input methods, such as nextInt or nextLine , then the method throws
an exception. If all goes well and there are no problems, such as using nextInt when the
input is not a correctly formed int , then the exception thrown will be NoSuchElement-
Exception . This throwing of a NoSuchElementException can be used to signal the
end of input. However, there is a more robust way of testing for the end of input
from a text file. Each of the input methods, such as nextInt and nextLine , has a
corresponding method, such hasNextInt and hasNextLine , that checks to see if
there is any more well-formed input of the appropriate type. The nice thing
about these methods is that they report when there is not a suitable next token
for any reason; they do not check only for the end of a file. For example,
hasNextInt returns false if there is no more file input of any kind or if the next
token is not a well-formed int value. It returns true if there is a well-formed int
as the next token.
A sample program that illustrates the use of hasNextLine to test for the end of
input is given in Display 10.4. A sample program that illustrates the use of hasNextInt
to test for the end of input is given in Display 10.5. A summary of some of the meth-
ods in the Scanner class is given in Display 10.6.
Checking for the End of a Text File with Scanner
You can check for the end of input with methods such as hasNextInt , hasNextLine , and
so forth.