输出个数最多的连续的字符

问题：

给定一个字符串，输出个数最多的连续的字符（不含空格）。

比如：

"this is a sentence" => [t, h, i, s, i, s, a, s, e, n, t, e, n, c, e]

"thiis iss a senntencee" => [i, s, n, e]
"thiisss iss a senntttenceee" => [s, t, e]
"thiisss iss a sennnntttenceee" =>

public class Solution {
public static void main(String[] args) {
String str = "thiisss iss a senntttenceee";
ArrayList<Character> list = new Solution().getMostFrequentChars(str);
for (Character c : list) {
System.out.print(c + " ");
}
}
public void add(ArrayList<Character> list, int count, int preMaxCount, char current) {
if (current == ' ') return;
if (count > preMaxCount) {
list.clear();
list.add(current);
} else if (count == preMaxCount) {
list.add(current);
}
}

public ArrayList<Character> getMostFrequentChars(String str) {
ArrayList<Character> list = new ArrayList<Character>();
if (str == null || str.length() == 0) return list;
char current = str.charAt(0);
int count = 1;
int preMaxCount = -1;
for (int i = 1; i < str.length(); i++) {
if (str.charAt(i) == current) {
count++;
} else {
if (count >= preMaxCount) {
add(list, count, preMaxCount, current);
if (current != ' ') preMaxCount = count;
}
current = str.charAt(i);
count = 1;
}
}
add(list, count, preMaxCount, current);
return list;
}
}