Longest Substring Without Repeating Characters

public class Solution {
    public int lengthOfLongestSubstring(String s) {
		// Start typing your Java solution below
		// DO NOT write main() function
		int start = 0, res = 0;
		int[] pos = new int[256];
        for(int i = 0; i < 256; i++)
			pos[i] = -1;
		for(int i = 0; i < s.length(); i++){
			char temp = s.charAt(i);
			if(start <= pos[(int)temp]){
				res = Math.max(res, i - start);
				start = pos[(int)temp] + 1;
			}
			pos[(int)temp] = i;
		}
		res = Math.max(res, s.length() - start);
		return res;
	}
}