not fast enough

Genomic Range codility lesson 3

import java.util.Arrays;
import java.util.HashMap;
class Solution {
    public int[] solution(String S, int[] P, int[] Q) {
        // write your code in Java SE 8
        int []result=new int[P.length];
        for(int index=0;index<P.length;index++){
           String check= S.substring(P[index],Q[index]+1);
           if(check.contains("A")){
           result[index]=1;
           }else if(check.contains("C")){
            result[index]=2;
           }else if(check.contains("G")){
            result[index]=3;
           }else{
            result[index]=4;
           }
        }
        return result;
    }
}