SnakeGameA.java

import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.LinkedList;

    public class SnakeGameA {
        public static void main(String[] args){
            // load the area into 2D char array
            char[][] area = loadAndGetArea();
            //check the arg if its just 2
            if(args.length !=2){
                System.out.println("command used: java SnakeGameA.java <direction> <Step> ");
                return;
            }
            //define the arg
            String direction = args[0];
            int step = Integer.parseInt(args[1]);

            //for the movement of directions in the area
            int directionRow = 0;//up/down
            int directionCol = 0;//left/right

            //what user enter in the arg
            if( direction.equals("up") ){
                directionRow = -1;//move one row up
            } else if(direction.equals("down")){
                System.out.println("Only open direction up,left.right");
                return;
            }else if(direction.equals("left")){
                directionCol =-1;
            }else if(direction.equals("right")){
                directionCol =1;
            }else {
                System.out.println("Invalid direction");
                return;
            }
            //used linkedList for snack body
            LinkedList<int[]> snake = findSnake(area);
            if(snake.isEmpty()){
                System.out.println("No snake find!");
                return;
            }
            //before move
            System.out.println("Game before move ");
            displayArea(area);
            //current head(rightmost) positions
            int[] CurrRightmost = snake.getLast();

            //movement for steps:

            for(int i = 0; i<step; i++){
                //1.calculate next positions:
                int nextRow = CurrRightmost[0] + directionRow;
                int nextCol = CurrRightmost[1] + directionCol;
                //this CurrRightmost functions return new head positions
                CurrRightmost = moveSnake(area, snake, CurrRightmost, new int[]{nextRow,nextCol});
            }
            //after move
            System.out.println("Game after move ");
            displayArea(area);

            //save updated area to file
            saveArea(area);
            //print lines for spices
            printEmptyLines();
        }
        //move snake from CurrRightmost to nextRightmost
        public static int[] moveSnake(char[][]area, LinkedList<int[]> snake, int[] CurrRightmost,int[] nextRightmost){
            int row = nextRightmost[0];
            int col = nextRightmost[1];

            //2.wall collision
            if(row<0 || row>=15 || col<0 || col>=15){
                System.out.println("wall collision ");
                return CurrRightmost;
            }

            //3.self collision
            //"i" here like counter of index go through parts of the snake
            for(int i = 0; i<snake.size(); i++){
                int[] part = snake.get(i);

                if(part[0] == row && part[1] == col ){
                    System.out.println("self collision ");
                    return CurrRightmost;
                }
            }
            //4.remove tail(leftmost)
            int[] leftmost = snake.removeFirst();
            area[leftmost[0]][leftmost[1]]= '-';//update grid area, after remove tail replace with "-"
            //5.add new head(rightmost)
            snake.addLast(nextRightmost);
            area[row][col]= 'o';
            return nextRightmost;//return new head positions
        }
        /*
        in this method will scan area(grid)+ collect
        cell that contain 'o'
         */
        public static LinkedList<int[]> findSnake(char[][] area){
            //create list to store snake body positions each p stores in array int[]
            LinkedList<int[]> snake = new LinkedList<>();
            //use this loop to check every cell in the area
            for (int row = 0; row < 15; row++) {
                for (int col = 0; col < 15; col++) {
                    if (area[row][col] == 'o') {//check if cell contain part of snake
                        snake.add(new int[]{row, col});//store positions into list
                    }
                }
            }
            return snake;//return snake body as list
        }
        //this print char[][]area
        public static void displayArea(char[][] area) {
            for (int row = 0; row < 15; row++) {//go through rows starts from 0-14 (15)
                for (int col = 0; col < 15; col++) {//go through cols starts from 0-14
                    System.out.print(area[row][col]);//will print char in that cell
                    if (col < 15 - 1) System.out.print(" ");//print space between cells
                    //(col < 15 - 1) avoid printing space after last col
                }
                System.out.println();
            }
        }
        //loadAndGetArea---> read & load file & convert content to char[15][15]
        public static char[][] loadAndGetArea() {
            char[][] area = new char[15][15];//2D
            try {
                //read the file as one string, (relativePath)--> location path
                String fileContent = Files.readString(Path.of(relativePath));
                //spilt it to lines
                String[] lines = fileContent.split("\n");
                //read each line of the file
                for (int row = 0; row < 15; row++) {
                    //split each row into cells
                    String[] cells = lines[row].trim().split(" ");
                    for (int col = 0; col < 15; col++) {
                        //cells it's an array of string not char, after split each
                        // element is string even contain but area stores char so convert
                        area[row][col] = cells[col].charAt(0);
                    }
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
            return area;
        }
        //FileWriter--> open the file to writing+ auto close the file
        public static void saveArea(char[][] area) {
            try (FileWriter fw = new FileWriter(relativePath)) {
                //scan every r+c
                for (int row = 0; row< 15; row++) {
                    for (int col = 0; col< 15; col++) {
                        //write char into file
                        fw.write(area[row][col]);
                        //add space between col
                        if (col < 15 - 1) fw.write(' ');
                    }
                    fw.write('\n');//new line for row
                }
                //if writes fails throw Runtime,stop program show an error message
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

        public static void printEmptyLines() {
            for (int count = 0; count < 18; count++) {
                System.out.println();
            }
        }
        public static final String relativePath = "./area.txt";
    }