java - 使用 StringTokenizer 计算字符

Question

我需要编写一个函数来计算字符串中每个字母的频率。

这是一个例子：

我收到文件：notes.txt 消息包括：“你好，这是来自内布拉斯加州的杰克”

当我阅读文件时，结果如下：

a: 3 H: 1 e: 2 l: 2 等

有人告诉我可以使用 Stringtokeizer，这是真的吗？

Answer 1

You could use a Multiset/Bag data structure approach. Using Guava it would look like:

public static void main(String... a) {
    final String str = "Hello this is Jack from Nebraska";

    final Builder<Character> b = ImmutableMultiset.builder();           
    for (char c : str.toCharArray())
        b.add(c);

    System.out.println(b.build());
}

Results in:

[H, e x 2, l x 2, o x 2, x 5, t, h, i x 2, s x 3, J, a x 3, c, k x 2, f, r x 2, m, N, b]

Answer 2

public static void main(String... args) {

    String str = "Hello this is Jack from Nebraska";

    Map<Character, Integer> frequencies = new HashMap<Character, Integer>();
    for (char c : str.toCharArray()) {
        if (!frequencies.containsKey(c))
            frequencies.put(c, 1);
        else
            frequencies.put(c, frequencies.get(c) + 1);
    }

    System.out.println(frequencies);
}

Output:

{f=1,  =5, e=2, b=1, c=1, a=3, o=2, N=1, l=2, m=1, H=1, k=2, h=1, J=1, i=2, t=1, s=3, r=2}