java编程题，OOP统计给定字符串每个字符出现的个数 "testat"

Question

Letter[] letters

class Letter{
String/char alpha;
int count;

alpha+""+count;
}
①构造数组并打印
②数组排序 (按照个数降序 字符升序)

Answer 1

String str ="2342asfghgyu56asdasda";
Map<String,Integer> maps = new HashMap<String,Integer>();
for(int i=0;i<str.length();i++){
String key = String.valueOf((str.charAt(i)));
if(!maps.containsKey(key))
maps.put(key, 1);
else{
int val =maps.get(key);
maps.put(key, val+1);
}

}

for(Map.Entry i : maps.entrySet()){
System.out.println(i.getKey()+ "=="+i.getValue());
}