File Processing - Building Java Programs: A Back to Basics Approach - page 381

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The line of code may seem correct because it mentions the name of the file,
but it won't work because it doesn't include the File object.
Normally, when you make a mistake like this Java warns you that you have
done something illegal. In this case, however, you'll get no warning from Java.
This is because, as you'll see later in this chapter, it is possible to construct a
Scanner from a String , in which case Java reads from the String itself.
If you were to make this mistake in the CountWords program, you would get
the following output:
total words = 1
The program would report just one word because the String "hamlet.txt"
looks like a single word to the Scanner . So, whenever you construct a Scanner
that is supposed to read from an input file, make sure that you include the call on
new File to construct an appropriate File object.
6.2 Details of Token-Based Processing
Now that we've introduced some of the basic issues involved in reading an input file, let's
explore reading from a file in more detail. One way to process a file is token by token.
Token-Based Processing
Processing input token by token (i.e., one word at a time or one number at
a time).
Recall from Chapter 3 the primary token-reading methods for the Scanner class:
• nextInt for reading an int value
• nextDouble for reading a double value
• next for reading the next token as a String
For example, you might want to create a file called numbers.dat with the follow-
ing content:
308.2 14.9 7.4
2.8
3.9 4.7 -15.4
2.8