Do any error Free Java program
Answers
Answer:
Recovering from Error is not possible. We can recover from exceptions by either using try-catch block or throwing exceptions back to caller. All exceptions occurs at runtime but checked exceptions are known to compiler while unchecked are not.
public class Cell {
final static int CELL_TYPE_EMPTY = 0, CELL_TYPE_FOOD = 10, CELL_TYPE_SNAKE_NODE = 20;
final int row, col;
int type;
public Cell(int row, int col) {
this.row = row;
this.col = col;
}
}
This class only keeps row and column numbers. Also some constant integers to determine the types of cells.
Our second class is Board.java. This class will allow us to identify the area where snake navigates (like a chessboard). Our class is as follows:
public class Board {
final int ROW_COUNT, COL_COUNT;
Cell[][] cells;
public Board(int rowCount, int columnCount) {
ROW_COUNT = rowCount;
COL_COUNT = columnCount;
cells = new Cell[ROW_COUNT][COL_COUNT];
for (int row = 0; row < ROW_COUNT; row++) {
for (int column = 0; column < COL_COUNT; column++) {
cells[row][column] = new Cell(row, column);
}
}
}
public void generateFood() {
int row = (int) (Math.random() * ROW_COUNT);
int column = (int) (Math.random() * COL_COUNT);
cells[row][column].type = Cell.CELL_TYPE_FOOD;
}
}
In this class, we are creating a two-dimensional array of the class "Cell" sized by rowCount * columnCount.
generatefood() is assigning the type of a random Cell to CELL_TYPE_FOOD.
Our third class is Snake.java.
public class Snake {
LinkedList<Cell> snakePartList = new LinkedList<>();
Cell head;
public Snake(Cell initPos) {
head = initPos;
snakePartList.add(head);
}
public void grow() {
snakePartList.add(head);
}
public void move(Cell nextCell) {
Cell tail = snakePartList.removeLast();
tail.type = Cell.CELL_TYPE_EMPTY;
head = nextCell;
snakePartList.addFirst(head);
}
public boolean checkCrash(Cell nextCell) {
for (Cell cell : snakePartList) {
if (cell == nextCell) {
return true;
}
}
return false;
}
}
Finally, our last class Router.java:
public class Router {
public static final int DIRECTION_NONE = 0, DIRECTION_RIGHT = 1, DIRECTION_LEFT = -1, DIRECTION_UP = 2, DIRECTION_DOWN = -2;
private Snake snake;
private Board board;
private int direction;
private boolean gameOver;
public Router(Snake snake, Board board) {
this.snake = snake;
this.board = board;
}
public void setDirection(int direction) {
this.direction = direction;
}
public void update() {
if (!gameOver) {
if (direction != DIRECTION_NONE) {
Cell nextCell = getNextCell(snake.head);
if (snake.checkCrash(nextCell)) {
setDirection(DIRECTION_NONE);
gameOver = true;
} else {
snake.move(nextCell);
if (nextCell.type == Cell.CELL_TYPE_FOOD) {
snake.grow();
board.generateFood();
}
}
}
}
}
private Cell getNextCell(Cell currentPosition) {
int row = currentPosition.row;
int col = currentPosition.col;
if (direction == DIRECTION_RIGHT) {
col++;
} else if (direction == DIRECTION_LEFT) {
col--;
} else if (direction == DIRECTION_UP) {
row--;
} else if (direction == DIRECTION_DOWN) {
row++;
}
Cell nextCell = board.cells[row][col];
return nextCell;
}
}
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