Reverse Prefix of Word

给一个word, 给一个char, 求这个word开始到char的substring的反转后的结果.

class Solution {
    public String reversePrefix(String word, char ch) {
        char[] chs = word.toCharArray();
        int ind = word.indexOf(ch);
        if(ind == -1)
            return word;
        int i = 0;
        int j = ind;
        while(i < j){
            swap(chs, i++, j--);
        }
        return String.valueOf(chs);
    }
    public void swap(char[] c, int i, int j){
        char t = c[i];
        c[i] = c[j];
        c[j] = t;
    }
}