Files.lines()to read file as stream
- Filter out lines which are not matching pattern "only whitespaces and numbers"
- Use map operation which will inside split the line by whitespace and convert that to stream (
Arrays.stream()can be useful, then use reduce operation to get numbers concatenated with "+", then use the same trick as above to calculate the sum of numbers and concatenate it with above string)
- Write each line to a file - just using