Question

This is from Sun’s tutorial’s exercise area so I suppose it is homework.

I know how to use a for loop to iterate the string, but I wish to learn arrays while I am at it and store them in so. This is what I got so far:

BufferedReader in = new BufferedReader(new FileReader("xanadu.txt"));
int c;
char letters[] = new char[27]; //26 + newline?

while((c = in.read()) != -1){
    letters[(char)c] += 1; //store in index, so letters['a'] = 4 etc..
}

Now for some reason (works in other languages), it does not cast int c to charproperly, and it enters letters[110] or something in decimal ascii instead, of course that is out of bounds of my array.

What way should I tackle THAT problem so I can have a nice index of chars?

Answer 1

Well, first of all, System.out.println((int) 'A'); will not give you 0 or 1, it will give you 65, so you should at least do letters[(char) c - 'A'] += 1.

Still though, you have only considered 27 letters, which only includes lower case? or upper case? no spaces? and so on…

You probably want to do something like

Map<Character, Integer> counts = new HashMap<Character, Integer>();

BufferedReader in = new BufferedReader(new FileReader("data.txt"));
int c;
while((c = in.read()) != -1) {
    int count = counts.containsKey((char) c) ? counts.get((char) c) : 0;
    counts.put((char) c, count + 1);
}