java - 如何统计文本中字符出现的次数？

Question

首先，以下代码运行一个包含 37.000 个字符的 txt 文件(工作正常)。我想计算每个角色出现的可能性。因此，为了实现该目标，我必须计算每个字母在 test.txt 文件中出现的次数。

File file = new File("test.txt");
        FileInputStream fileStream = new FileInputStream(file);
        InputStreamReader input = new InputStreamReader(fileStream);
        BufferedReader reader = new BufferedReader(input);

        String line;

        // Initializing counters
        int countWord = 0;
        int sentenceCount = 0;
        int characterCount = 0;
        int whitespaceCount = 0;
        int a,b,c,d,e,f,g,h,i,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z=0;

        // Reading line by line from the
        // file until a null is returned
        while((line = reader.readLine()) != null) {
            if(!(line.equals(""))) {
                characterCount += line.length();


                // \\s+ is the space delimiter in java
                String[] wordList = line.split("\\s+");

                countWord += wordList.length;
                whitespaceCount += countWord -1;

                // [!?.:]+ is the sentence delimiter in java
                String[] sentenceList = line.split("[!?.:]+");

                sentenceCount += sentenceList.length;
            }
        }

        System.out.println("Total number of characters = " + characterCount);
        System.out.println("Total number of whitespaces = " + whitespaceCount);
 }

我正在考虑以下代码，但我确信代码更短，效率更高。

while((line = reader.readLine()) != null)
  if(!(line.equals(""))) {
    characterCount += line.length();
    if (line.equals("a")){
        a++;
    }...
  //same for the rest letters.

Answer 1

创建按字符键控的 map 非常简单。

1. Files.lines 接受输入文件并读取行。
2. flatMap 将行映射到字符流
3. 然后，字符按字符/计数的键/值对进行分组。

        Map<String, Long> freq = null;
        try {
        freq = Files.lines(Path.of("testfile.txt"))
                .flatMap(line -> Arrays.stream(line.split("")))
                .filter(str -> str.length() > 0)
                .collect(Collectors.groupingBy(chr -> chr,
                        Collectors.counting()));
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }

本声明

        freq.forEach((ch,cnt)->
           System.out.println("char = " + ch +"(" + 
                 Integer.toHexString(ch.charAt(0)) + ")" + " count = " + cnt));

打印与此类似的内容，并提供十六进制值。

char =  (20) count = 10
char = a(61) count = 4
char = r(72) count = 1
char = s(73) count = 9
char = d(64) count = 2
char = t(74) count = 8
char = e(65) count = 3
char = h(68) count = 4
char = i(69) count = 6
char = .(2e) count = 2
char = n(6e) count = 3
char = o(6f) count = 2