SeaShell

package com.company;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;

public class Seashell {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);


        List<String> collectedSeashell = new LinkedList<>();
        List<String> stolenSeashell = new LinkedList<>();

        int n = Integer.parseInt(scanner.nextLine());

        String [][] matrix = new String[n][];

        for (int i = 0; i<n; i++) {
            matrix [i] = scanner.nextLine().split("\\s+");
        }

        String input = scanner.nextLine();
        int count = 0;

        while (!input.equals("Sunset")) {
            String [] tokens = input.split(" ");

            int row = Integer.parseInt(tokens[1]);
            int col = Integer.parseInt(tokens[2]);

            switch (tokens[0]) {

                case "Collect":
                if (isValidIndex(matrix, row, col)) {
                    String shell = matrix[row][col];
                    if (!shell.equals("-")) {
                        collectedSeashell.add(shell);
                        matrix[row][col] = "-";
                    }

                }
                    break;
                case "Steal":
                    if (isValidIndex(matrix, row, col)) {
                        String shell = matrix[row][col];

                        String direction = tokens[3];


                        switch (direction) {
                            case "up":
                                for (int i = row; i>=row -3; i--) {
                                    if (isValidIndex(matrix, i, col)) {
                                    if (!shell.equals("-")) {
                                        stolenSeashell.add(shell);
                                        matrix[i][col] ="-";
                                        count++;
                                        }
                                    }
                                }
                                break;
                                case "down":
                                for (int i = row; i<=row +3; i++) {
                                    if (isValidIndex(matrix, i, col)) {
                                    if (!shell.equals("-")) {
                                        stolenSeashell.add(shell);
                                        matrix[i][col] ="-";
                                        count++;
                                        }
                                    }
                                }
                                break;
                                case "left":
                                for (int i = col; i>=col -3; i--) {
                                    if (isValidIndex(matrix, row, i)) {
                                    if (!shell.equals("-")) {
                                        stolenSeashell.add(shell);
                                        matrix[row][i] ="-";
                                        count++;
                                        }
                                    }
                                }
                                break;
                                case "right":
                                for (int i = col; i<=col +3; i++) {
                                    if (isValidIndex(matrix, row, i)) {
                                    if (!shell.equals("-")) {
                                        stolenSeashell.add(shell);
                                        matrix[row][i] ="-";
                                        count++;
                                        }
                                    }
                                }
                                break;
                        }
                    }

                    break;
            }
            input = scanner.nextLine();
        }
        printMatrix(matrix);

        System.out.printf("Collected seashells: %d", collectedSeashell.size());
        if (!collectedSeashell.isEmpty()) {
            System.out.print(" -> ");
            System.out.println(String.join(", ", collectedSeashell));
        } else {
            System.out.println();
        }

        System.out.println("Stolen seashells: " + stolenSeashell.size());
    }

    private static void printMatrix(String[][] matrix) {
        for (int row = 0; row<matrix.length; row++) {
            for (int col = 0; col<matrix[row].length; col++) {
                System.out.print(matrix[row][col] + " ");
            }
            System.out.println();
        }
    }

    private static boolean isValidIndex(String[][] matrix, int row, int col) {
        if (row>=0 && row < matrix.length) {
            if (col >=0 && col < matrix[row].length) {
                return true;
            }
        }
        return false;
    }
}