java - 计算文件中每个字符的个数

Question

我正在逐个字符地读取文本文件的内容，然后按升序对它们进行排序并计算每个字符出现的次数。当我运行程序时，我的数字偏离了方向，例如文件中有 7 个“A”，但我得到了 17。我认为这意味着我的计数有问题，或者我正在阅读的方式字符。有什么问题吗？

public class CharacterCounts {

    public static void main(String[] args) throws IOException{
        String fileName = args[0];
        BufferedReader in = new BufferedReader(new FileReader(new File(fileName)));
        ArrayList<Character> vals = new ArrayList<Character>();
        ArrayList<Integer> valCounts = new ArrayList<Integer>();

        while(in.read() != -1){
            vals.add((char)in.read());
        }

        Collections.sort(vals);

        //This counts how many times each char occures,
        //resets count to 0 upon finding a new char.
        int count = 0;
        for(int i = 1; i < vals.size(); i++){
            if(vals.get(i - 1) == vals.get(i)){
                count++;
            } else {
                valCounts.add(count + 1);
                count = 0;
            }
        }

        //Removes duplicates from vals by moving from set then back to ArrayList
        Set<Character> hs = new HashSet<Character>();
        hs.addAll(vals);
        vals.clear();
        vals.addAll(hs);

        //System.out.print(vals.size() + "," + valCounts.size());

        for(int i = 0; i < vals.size(); i++){
            //System.out.println(vals.get(i));
            System.out.printf("'%c' %d\n", vals.get(i), valCounts.get(i));
        }

    }
}

Answer 1

当你写的时候

if(vals.get(i - 1) == vals.get(i)){

两者是完全不同的引用，它们根本不相等。你必须比较它们的值(value)。

你想要

if(vals.get(i - 1).equals(vals.get(i))){