面试算法_出现次数最多的字母(含大小写)

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;

public class Q_3 {
public static void main(String[] args) {
// TODO Auto-generated method stub
String in="abcAAB";
find(in);
}

static void find(String in){
Map<Character, Integer> map = new TreeMap<>();

for(int i=0;i<in.length();i++){
char ch=in.charAt(i);
if('a'<=ch && ch<='z'){
ch = (char) (ch - 'a'+'A');
}
if(map.containsKey(ch)){
map.put(ch, map.get(ch)+1);
}
else{
map.put(ch, 1);
}
}
int max=0;
char t = ' ';
Iterator iterator=map.keySet().iterator();
while(iterator.hasNext()){
Character character = (Character) iterator.next();
System.out.println(character+":"+map.get(character));
if(map.get(character)>max){
max = map.get(character);
t = character.charValue();
}
}
System.out.println(t);
for(int i=0;i<in.length();i++){
if(in.charAt(i)==t || in.charAt(i)==(t-'A'+'a')){
System.out.print(in.charAt(i));
}
}
}
}