0187 Repeated DNA Sequences

Question

My Solution:

class Solution {
    public List<String> findRepeatedDnaSequences(String s) {
        Set<String> seen = new HashSet<>();
        Set<String> repeated = new HashSet();

        for(int i = 0; i+9 < s.length(); i++){
            String temp = s.substring(i, i+10);
            if(!seen.add(temp)){
                repeated.add(temp);
            }
        }

        return new ArrayList(repeated);
    }
}