一天一个类 --- StringTokenizer

    public StringTokenizer(String str, String delim, boolean returnDelims) {
        currentPosition = 0;
        newPosition = -1;
        delimsChanged = false;
        this.str = str;
        maxPosition = str.length();
        delimiters = delim;
        retDelims = returnDelims;
        setMaxDelimCodePoint();
    }

    public StringTokenizer(String str, String delim) {
        this(str, delim, false);
    }

    public boolean hasMoreTokens() {
        /*
         * Temporarily store this position and use it in the following
         * nextToken() method only if the delimiters haven‘t been changed in
         * that nextToken() invocation.
         */
        newPosition = skipDelimiters(currentPosition);
        return (newPosition < maxPosition);
    }

 1     public String nextToken() {
 2         /*
 3          * If next position already computed in hasMoreElements() and
 4          * delimiters have changed between the computation and this invocation,
 5          * then use the computed value.
 6          */
 7 
 8         currentPosition = (newPosition >= 0 && !delimsChanged) ?
 9             newPosition : skipDelimiters(currentPosition);
10 
11         /* Reset these anyway */
12         delimsChanged = false;
13         newPosition = -1;
14 
15         if (currentPosition >= maxPosition)
16             throw new NoSuchElementException();
17         int start = currentPosition;
18         currentPosition = scanToken(currentPosition);
19         return str.substring(start, currentPosition);
20     }

    public String nextToken(String delim) {
        delimiters = delim;

        /* delimiter string specified, so set the appropriate flag. */
        delimsChanged = true;

        setMaxDelimCodePoint();
        return nextToken();
    }

    public int countTokens() {
        int count = 0;
        int currpos = currentPosition;
        while (currpos < maxPosition) {
            currpos = skipDelimiters(currpos);
            if (currpos >= maxPosition)
                break;
            currpos = scanToken(currpos);
            count++;
        }
        return count;
    }