[FIXED] How to get a grid from list of strings?

Issue

I'm trying to filter a list of strings which contains information about grid and grid. I have a pattern of letters which can be used to build a grid. So, how to get this grid using pattern?

4 3
AABC
CABB
ACCA
2,1; 0,0; 3,0;

I have to execute only grid (strings with letters) using pattern ABC as new list.

The result should be:

AABC
CABB
ACCA

My code:

List<String> data = Files.lines(Path.of("src/main/resources/file.txt")).collect(Collectors.toList());
List<String> grid = new ArrayList<>();

String pattern = "ABC";

data.forEach(System.out::println);

for(int i = 0; i <= data.size(); i++){
    int finalI = i;
   grid = data.stream().filter(s -> s.startsWith(pattern.split("")[finalI])).collect(Collectors.toList());
}
grid.forEach(System.out::println);

It's not filtering and throws index out of bounds.

Solution

If I understand it correctly, you want only the strings (the lines from your file) that contain only the letters you specify. If so, just create a charachter class with the valid letters and filter using String.matches:

List<String> data = Files.readAllLines(Path.of("src/main/resources/file.txt"));

String regex = "[ABC]+";

List<String> grid = data.stream()
                        .filter(str -> str.matches(regex))
                        .collect(Collectors.toList());

grid.forEach(System.out::println);

Answered By - Eritrean
Answer Checked By - David Goodson (JavaFixing Volunteer)