The given code finds the digits from the given string that consists of letters also and calculate the sum of digits.

class CalculateSumFromString 
{
    public static void main(String[] args) 
    {
        String st="7 A B Z 6 2 ";
        String str=st.replace(" ","");
        char ch[]=str.toCharArray();
        int sum=0;
        for(int i=0;i<ch.length;i++){
        if(Character.isDigit(ch[i])){
            String s = Character.toString(ch[i]);
            int num = Integer.parseInt(s);
            sum+=num;
        }
        }
        System.out.println(sum);

    }
}