Cannot meet the forth requirement.
package zh.codegym.task.task18.task1821;
import java.io.*;
import java.util.*;
/*
符号频率
*/
public class Solution {
public static void main(String[] args) throws Exception {
String fileName = args[0];
BufferedReader fr = new BufferedReader(new FileReader(fileName));
String str;
List<Character> chList = new ArrayList<>();
while ((str = fr.readLine()) != null) {
char[] arr = str.toCharArray();
for(char ch : arr)
chList.add(ch);
}
fr.close();
Set<Character> set = new HashSet<>(chList);
Map<Character, Integer> map = new HashMap<>();
for (char ch : set) {
int count = Collections.frequency(chList, ch);
map.put(ch, count);
}
TreeMap sortedMap = new TreeMap(map);
for (Map.Entry<Character, Integer> entry : map.entrySet()) {
System.out.println(entry.getKey() + " " + entry.getValue());
}
}
}