Java小demo-使用Collection统计字符串每个字出现的次数

package com.stevenwong.package5;

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

public class CounterWordDemo {
    public static void main(String[] args) {
        String str = "Hello World!";
        char[] charArray = str.toCharArray();
        HashMap<Character, Integer> counterMap = new HashMap<>();
        for (char c : charArray) {
            Integer count = counterMap.get(c);
            if (count == null) {
                counterMap.put(c, 1);
            } else {
                counterMap.put(c, ++count);
            }
        }
        for (Map.Entry<Character, Integer> entry : counterMap.entrySet()) {
            System.out.println(entry.getKey() + " : " + entry.getValue());
        }
    }
}

  : 1
! : 1
r : 1
d : 1
e : 1
W : 1
H : 1
l : 3
o : 2