To open the file, a FileInputStream is used, and to turn the file into words a StreamTokenizer is created from the FileInputStream. In StreamTokenizer, there is a default list of separators, and you can add more with a set of methods. Here, ordinaryChar( ) is used to say “This character has no significance that I’m interested in,” so the parser doesn’t include it as part of any of the words that it creates. For example, saying st.ordinaryChar('.') means that periods will not be included as parts of the words that are parsed. You can find more information in the online documentation that comes with Java. 

In countWords( ), the tokens are pulled one at a time from the stream, and the ttype information is used to determine what to do with each token, since a token can be an end-of-line, a number, a string, or a single character. 

Once a token is found, the Hashtable counts is queried to see if it already contains the token as a key. If it does, the corresponding Counter object is incremented to indicate that another instance of this word has been found. If not, a new Counter is created – since the Counter constructor initializes its value to one, this also acts to count the word. 

SortedWordCount is not a type of Hashtable, so it wasn’t inherited. It performs a specific type of functionality, so even though the keys( ) and values( ) methods must be re-exposed, that still doesn’t mean that inheritance should be used since a number of Hashtable methods are inappropriate here. In addition, other methods like getCounter( ), which get the Counter for a particular String, and sortedKeys( ), which produces an Enumeration, finish the change in the shape of SortedWordCount’s interface. 

In main( ) you can see the use of a SortedWordCount to open and count the words in a file – it just takes two lines of code. Then an enumeration to a sorted list of keys (words) is extracted, and this is used to pull out each key and associated Count. Note that the call to cleanup( ) is necessary to ensure that the file is closed