正在扫描字符错误？

Question

I'm scanning a file and trying to track the amount of times a character comes up.

public static Map<Character, Integer> getCountMap(Scanner in){
    Map<Character, Integer> wordCountMap = new TreeMap<Character, Integer>();

    while (in.hasNext()){
        Character word = in.next().toLowerCase();
        //CHAR HAS BEEN SEEN, ADD
        if(wordCountMap.containsKey(word)){
            int count = wordCountMap.get(word);
            wordCountMap.put(word, count + 1);
        }
        //NEW CHAR, CREATE
        else    {
            wordCountMap.put(word, 1);
        }
    }
return wordCountMap;
}

I'm getting an error for Character word = in.next().toLowerCase();

I checked java api, and characters definitely have access to toLowerCase() . However the api for Scanners says

hasNext() Returns true if this scanner has another token in its input.

Does that mean a scanner can't scan through per character? Shouldn't this just scan through the characters, adding them to the map and increasing the count each time it see's something?

Final note : This code runs just fine if every Character is replaced with String . I can get a word count no problem. Char count, not so much.

Main Method (In case this is required)

public static void main(Character[] args) throws FileNotFoundException{

    //read the book into the map
    Scanner in = new Scanner(new File("moby.txt"));
    Map<Character, Integer> wordCountMap = getCountMap(in);


    for (Character word: wordCountMap.keySet()){
        int count = wordCountMap.get(word);
        if (count > OCCURRENCES){
            System.out.println(word + " occurs " + count + " times.");
        }
    }

}

Answer 1

According to the Javadocs for the next() method of java.util.Scanner :

 public String next() 

Finds and returns the next complete token from this scanner. A complete token is preceded and followed by input that matches the delimiter pattern.

As can be seen, this method does not return Character ; it returns String , which is why you're getting that error.

A token is basically a substring that falls between two instances of a delimiter. The default delimiter of a Scanner is a whitespace object ( \\s , \\t , \\n , etc.). So the Scanner goes through the file and each invocation of next() will return the next sequence of characters that is between what is seen as a delimiter.

So what you could do is change the delimiter so that the Scanner counts each character in the file as a token, though that's a bit complex. What you could do instead is make use of the fact that the String class has a method toCharArray() , which returns the sequence of characters in the string as an array. You can count the individual characters a lot easier that way:

String word = in.next().toLowerCase();
char[] charsInWord = word.toCharArray();
// ...