Question

I have a text file that reads:

1 2 3 4 5

6 7 8 9 1

8 3 9 7 1

9 3 4 8 2

8 7 1 6 5

where each number is separated by a tab.

My question is, is there a simple way to sum the columns of numbers using java? I want it to sum 1+6+8+9+8, 2+7+3+3+7, etc. I am reading the file using:

 public static boolean testMagic(String pathName) throws IOException {
    // Open the file
    BufferedReader reader = new BufferedReader(new FileReader(pathName));

    // For each line in the file ...
    String line;
    while ((line = reader.readLine()) != null) {
        // ... sum each column of numbers
        }

    reader.close();
    return isMagic;
}

public static void main(String[] args) throws IOException {
    String[] fileNames = { "MyFile.txt" };

}

Answer 1

is the number of columns known or variable? You can just create an array of sums and parse each line into ints and the add it to the correct sum.

// For each line in the file ...
String line;
int sums[5]; //Change to the number of columns
while ((line = reader.readLine()) != null) {
    String tokens[] = line.split("\t");
    for(int i = 0; i < 5; i++)
    {
       sums[i] += Integer.parseInt(tokens[i]);
    }
 }

If you don’t know the number of columns beforehand use an ArrayList and do the first line differently so that you can figure out the number of columns.