ROITI Find sum of numbers in String O(n)/O(n^2)

public class Digits {

    public static double getDigits(String s){
        double sum = 0;
        String temp = "";
        CharSequence seq = ".";
        for (int i = 0; i < s.length(); i++) {
            if((Character.isDigit(s.charAt(i)) || s.charAt(i) == '.') && i!=s.length()-1){
                if(temp=="" && s.charAt(i) == '.'){
                    continue;
                } else if(temp.contains(seq) && s.charAt(i) == '.') throw new NumberFormatException("Unformatted Input");
                // this check makes the algorithm O(n^2) in the worst possible case, otherwise it is O(n)
                // it is not O(n(nm)) (Boyer-Moore) , because the char sequence is only '.'
                temp+=s.charAt(i);
            } else {
                if(Character.isDigit(s.charAt(i)) && i==s.length()-1) temp+=s.charAt(i);
                try{sum+=Double.parseDouble(temp);}
                catch(Exception e){}
                temp="";
            }
        }
        return sum;
    }


    public static void main(String[] args){
        String s = "2 beers0.5 or not 12.3 beers.5";
        try{
        System.out.println(getDigits(s));
        } catch(Exception e){
            System.out.println(e.getMessage());
        }
    }
}