java 實現統計字母個數，並輸出最多的字母

import java.util.HashMap;
import java.util.Set;
import java.util.Map;

public class Test {

    public static void main(String args[]) {
        Map<Character, Integer> map = new HashMap<>();
        String str = "today is a special day";
        for(int i = 0; i < str.length(); i++) {
            if(map.containsKey(str.charAt(i)))
                map.put(str.charAt(i), map.get(str.charAt(i))+1);
            else
                map.put(str.charAt(i), 1);
        }
        Set<Character> set = map.keySet();
        int max1 = -0xf3f3f3f;
        for(Character key : set)
            if(Character.isAlphabetic(key)) {
                max1 = Math.max(map.get(key), max1);
            }
        System.out.println(max1);
    }
}