Check If a String Contains All Binary Codes of Size K.java

class Solution {
    public boolean hasAllCodes(String s, int k) {
        HashSet<String> hs=new HashSet();
        for(int i=0;i<=s.length()-k;i++){
            hs.add(s.substring(i,i+k));
        }
        if(hs.size() == Math.pow(2,k))return true;
        return false;
    }
}