Map(5)--用集合统计字符串中字符出现的次数

public static void main(String[] args) {
String s="aaaabbbbbbbccccccc";
char[] arr=s.toCharArray();
HashMap<Character, Integer> hm=new HashMap<Character, Integer>();
for (char c : arr) {
/*if(!hm.containsKey(c)){//如果不包含这个健，就将该字符当作健，值为1存储
hm.put(c, 1);
}else{
hm.put(c, c.get(c)+1);
}*/
hm.put(c, !hm.containsKey(c)?1:hm.get(c)+1);//优化算法

}
for (Character key : hm.keySet()) {
System.out.println(key+"="+hm.get(key));
}
}

b=7
c=7
a=4