最长不含重复字符的字符号串

class Solution {
    public int lengthOfLongestSubstring(String s) {
     if(s.length()==0) return 0;   
//双指针(r指针最先向右移动，遇到重复的l指针向右移动直到越过重复的r指针继续向右移动)
    int l=0,r=0,res=0;
    Map<Character,Integer> map = new HashMap<>();
    while(l<=r){
        char ch_r = s.charAt(r);
        map.put(ch_r,map.getOrDefault(ch_r,0)+1);
        while(map.get(ch_r)>1){
            char ch_l = s.charAt(l);
            map.put(ch_l,map.getOrDefault(ch_l,0)-1);
            l++;
        }
        res = res > r-l+1? res:r-l+1;
        r++;
        if(r==s.length()) break;

    }
    return res;
    }
}