Java-如何更改名称为字符串的变量

Question

Okay, perhaps that was a little hard to understand.

I'm trying to count all the letters in a string and eventually print all the counts, and I'd like to know how to change the count of a character in my loop.

Currently it goes like this:

for (int i = 0; i<line.length();i++){
    line.charAt(i)++;
}

I have all the variable names as one character which they each represent, as in: int a=0,b=0,c=0,d=0,e=0,f=0 etc

How do I use the ++ operator in this situation? line.charAt(iter) gives me a character, but how do I use that character as a variable?

Answer 1

This is not possible.

To do it correctly you should use a Map . Store all this letters in a map of type Map<Character, Integer> . Then you can update values like this:

// assumming your data looks like this:
Map<Character, Integer> map = new HashMap<>();
map.put('a', 0);
map.put('b', 0);
// etc..., you should probably init these in a loop


// then you can do
for (int i = 0; i<line.length();i++){
    map.compute(line.charAt(i), i -> i+1);
}

Answer 2

You could collect the counts using an int array.

int[] counts = new int[256];
for (int i = 0; i < line.length(); i++){
    counts[line.charAt(i)]++;
}
a = counts['a'];
b = counts['b'];
...

Answer 3

If you're dealing with only lowercase letters, you can keep an array of counts for an old school "C style" approach:

int[] counts = new int[26];

then in your loop:

counts[line.charAt(i) - 'a']++;

---

Alternatively, there's the easier, 1-line way:

Map<Integer, Long> frequency = line.chars().boxed().collect(Collectors.groupingBy(i -> i, Collectors.counting()));

Where the key of the map is the integer value of the char.