3. 无重复字符的最长子串

class Solution {
    public int lengthOfLongestSubstring(String s) {
        if(s==null||s.length()==0){
            return 0;
        }
        Set<Character> set=new HashSet<>();
        int max=0;
        int current=0;
        for(int i=0;i<s.lenght();i++){
            while(current<=i&&!set.containsKey(s.charAt(i))){
                set.
                current++;
            }
        }
    }
}