Creating a tab-delimited .txt table from an ArrayList<String> matrix

Question

I am currently working on the creation of a tab-delimited table for Excel from an ArrayList<String> matrix in Java.

The matrix is a List<List<String> and currently I am adding "\t" to every single String in the matrix and "\n" to the last elements of each row. I use for loops to do so.

For a 1500 x 3000 matrix this process takes an insane amount of time (120s).

What is a better way too approach this problem in order to cut down on time?

Answer 1

Not sure which way your matrix is but could be built something like this I suppose. Dont see any obvious overhead here.

private final List<List<String>> matrix;
private final String SEPARATOR = "\t";
private final String END_OF_LINE = "\n";

public TSVFormatter(List<List<String>> matrix) {
    this.matrix = matrix;
}

public String doParse() {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < matrix.size(); i++) {
        for (int o = 0; o < matrix.get(i).size(); o++) {
            sb.append(matrix.get(i).get(o));
            if (o <( matrix.get(i).size()-1))
                sb.append(SEPARATOR);
            else
                sb.append(END_OF_LINE);
        }
    }
    return sb.toString();
}