File Processing - Building Java Programs: A Back to Basics Approach - page 380

Common Programming Error
Reading Beyond the End of a File
As you learn how to process input files, you are likely to write programs that
accidentally attempt to read data when there is no data left to read. For example,
the CountWords program we just saw uses a while loop to keep reading words
from the file as long as there are still words left to read. After the while loop,
you might include an extra statement to read a word:
while (input.hasNext()) {
String word = input.next();
count++;
}
String extra = input.next(); // illegal, no more input
This new line of code causes the computer to try to read a word when there is
no word to read. Java throws an exception when this occurs:
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:817)
at java.util.Scanner.next(Scanner.java:1317)
at CountWords.main(CountWords.java:15)
As usual, the most important information appears at the end of this list of line
numbers. The exception indicates that the error occurred in line 15 of CountWords .
The other line numbers come from the Scanner class and aren't helpful.
If you find yourself getting a NoSuchElementException , it is probably because
you have somehow attempted to read beyond the end of the input. The Scanner is
saying, “You've asked me for some data, but I don't have any such value to give you.”
Common Programming Error
Forgetting "new File"
Suppose that you intend to construct a Scanner the way we've learned:
Scanner input = new Scanner(new File("hamlet.txt"));
But you accidentally forget to include the File object and instead write this line
of code:
Scanner input = new Scanner("hamlet.txt"); // not right
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