Check if Numbers Are Ascending in a Sentence

class Solution {
    public boolean areNumbersAscending(String s) {
        String[] strs = s.split(" ");
        int n = -1;
        for(String ss : strs){
            if(isNum(ss)){
                int m = Integer.valueOf(ss);
                if(n >= m)
                    return false;
                n = m;
            }
        }
        return true;
    }
    
    public boolean isNum(String s)
    {
        for(char c : s.toCharArray())
            if(!Character.isDigit(c))
                return false;
        return true;
    }
}