Battleship game board in Java

I write the code of the warships game. There are two players, human and computer players. Both of them have separate boards. In the beginning, I automatically place the ships on both boards randomly, then I take the coordinates and put the ships on each other's boards.If the place in the coordinate hits the other player's ship, I will send a message saying this to the screen. The character "s" is shown on the screen if it sinks the ship, only with "*" if it hits and "x" if it cannot hit. How can I make changes to the computer player's board after receiving coordinates when it's time for the human player?

public static int numRows = 10;
public static int numCols = 10;
public static int playerShips;
public static int computerShips;
public static String[][] grid = new String[numRows][numCols];
public static int[][] missedGuesses = new int[numRows][numCols];
public static void main(String[] args) {
System.out.println("Welcome to Amiral Batti game");
System.out.println("\nComputer: ");
deployComputerShips();
System.out.println("\n");
System.out.println("\nHuman: ");
deployPlayerShips();
do {
Battle();
}
while(players.playerShips != 0 && players.computerShips != 0);
gameOver();
}
public static int FIELD_SIZE = 10;
public static void deployPlayerShips() {
Random random = new Random();
int[][] field = new int[FIELD_SIZE][FIELD_SIZE];
for (int i = 5; i > 0; i--) {
int x = random.nextInt(field.length);
int y = random.nextInt(field.length);
boolean vertical = random.nextBoolean();
if (vertical) {
if (y + i > FIELD_SIZE) {
y -= i;
}
} else if (x + i > FIELD_SIZE) {
x -= i;
}
boolean isFree = true;
if (vertical) {
for (int m = y; m < y + i; m++) {
if (field[m][x] != 0) {
isFree = false;
break;
}
}
} else {
for (int n = x; n < x + i; n++) {
if (field[y][n] != 0) {
isFree = false;
break;
}
}
}
if (!isFree) {
i++;
continue;
}
if (vertical) {
for (int m = Math.max(0, x - 1); m < Math.min(FIELD_SIZE, x + 2); m++) {
for (int n = Math.max(0, y - 1); n < Math.min(FIELD_SIZE, y + i + 1); n++) {
field[n][m] = 9;
}
}
} else {
for (int m = Math.max(0, y - 1); m < Math.min(FIELD_SIZE, y + 2); m++) {
for (int n = Math.max(0, x - 1); n < Math.min(FIELD_SIZE, x + i + 1); n++) {
field[m][n] = 9;
}
}
}
for (int j = 0; j < i; j++) {
field[y][x] = i;
if (vertical) {
y++;
} else {
x++;
}
}
}
System.out.print(" ");
System.out.println("0 1 2 3 4 5 6 7 8 9");
char[][] map = new char[FIELD_SIZE][FIELD_SIZE];
for (int i = 0; i < FIELD_SIZE; i++) {
for (int j = 0; j < FIELD_SIZE; j++) {
map[i][j] = field[i][j] == 0 || field[i][j] == 9 ? '.' : 'o';
}
}
Arrays.stream(map)
.forEach(m -> System.out.println(Arrays.toString(m).replace(",", "")));
}
public static void deployComputerShips() {
Random random = new Random();
int[][] field = new int[FIELD_SIZE][FIELD_SIZE];
for (int i = 5; i > 0; i--) {
int x = random.nextInt(field.length);
int y = random.nextInt(field.length);
boolean vertical = random.nextBoolean();
if (vertical) {
if (y + i > FIELD_SIZE) {
y -= i;
}
} else if (x + i > FIELD_SIZE) {
x -= i;
}
boolean isFree = true;
if (vertical) {
for (int m = y; m < y + i; m++) {
if (field[m][x] != 0) {
isFree = false;
break;
}
}
} else {
for (int n = x; n < x + i; n++) {
if (field[y][n] != 0) {
isFree = false;
break;
}
}
}
if (!isFree) {
i++;
continue;
}
if (vertical) {
for (int m = Math.max(0, x - 1); m < Math.min(FIELD_SIZE, x + 2); m++) {
for (int n = Math.max(0, y - 1); n < Math.min(FIELD_SIZE, y + i + 1); n++) {
field[n][m] = 9;
}
}
} else {
for (int m = Math.max(0, y - 1); m < Math.min(FIELD_SIZE, y + 2); m++) {
for (int n = Math.max(0, x - 1); n < Math.min(FIELD_SIZE, x + i + 1); n++) {
field[m][n] = 9;
}
}
}
for (int j = 0; j < i; j++) {
field[y][x] = i;
if (vertical) {
y++;
} else {
x++;
}
}
}
System.out.print(" ");
System.out.println("0 1 2 3 4 5 6 7 8 9");
char[][] map = new char[FIELD_SIZE][FIELD_SIZE];
for (int i = 0; i < FIELD_SIZE; i++) {
for (int j = 0; j < FIELD_SIZE; j++) {
map[i][j] = field[i][j] == 0 || field[i][j] == 9 ? '.' : 'o';
}
}
Arrays.stream(map)
.forEach(m -> System.out.println(Arrays.toString(m).replace(",", "")));
}
public static void Battle(){
playerTurn();
computerTurn();
printBoard();
System.out.println();
System.out.println("Your ships: " + players.playerShips + " | Computer ships: " + players.computerShips);
System.out.println();
}
public static void playerTurn(){
Scanner scn = new Scanner(System.in);
System.out.println("\nHuman's turn: ");
int x = -1, y = -1;
do {
Scanner input = new Scanner(System.in);
System.out.print("Enter row number: ");
x = scn.nextInt();
System.out.print("Enter column number: ");
y = scn.nextInt();
if ((x >= 0 && x < numRows) && (y >= 0 && y < numCols)){
if (grid[x][y].equals("o")){
System.out.println("You sunk the ship!");
grid[x][y] = "s";
--players.computerShips;
}
else if (grid[x][y].equals(".")) {
System.out.println("You missed");
grid[x][y] = "x";
}
}
else if ((x < 0 || x >= numRows) || (y < 0 || y >= numCols))
System.out.println("You can't place ships outside the " + numRows + " by " + numCols + " grid");
}
while((x < 0 || x >= numRows) || (y < 0 || y >= numCols));
}
public static void computerTurn(){
System.out.println("\nComputer's turn: ");
int x = -1, y = -1;
do {
x = (int)(Math.random()*10);
y = (int)(Math.random()*10);
System.out.println("Enter row number: "+x);
System.out.println("Enter column number: "+y);
if ((x >= 0 && x < numRows) && (y >= 0 && y < numCols)){
if (grid[x][y].equals("o")){
System.out.println("The Computer sunk one of your ships!");
grid[x][y] = "s";
--players.playerShips;
++players.computerShips;
}
else if (grid[x][y].equals(".")) {
System.out.println("Computer missed");
grid[x][y] = "x";
if(missedGuesses[x][y] != 1)
missedGuesses[x][y] = 1;
}
}
}
while((x < 0 || x >= numRows) || (y < 0 || y >= numCols));
}
public static void gameOver(){
System.out.println("Your ships: " + players.playerShips + " | Computer ships: " + players.computerShips);
if(players.playerShips > 0 && players.computerShips <= 0)
System.out.println("You won the battle! ");
else
System.out.println("You lost the battle! ");
System.out.println();
}
public static void printBoard(){
System.out.print(" ");
System.out.println("0123456789");
for(int x = 0; x < grid.length; x++) {
System.out.print(x);
for (int y = 0; y < grid[x].length; y++){
System.out.print(grid[x][y]);
}
System.out.println();
}
System.out.println();
}

Okay here is a more correct version. I could do more but ... then half of the code would be rewritten and I don't see the point of doing that (doesn't help you). So I insist that its far from perfect but at least it resolves your issue. I made the following corrections:

• The battle() method has a corrected game logic
• I removed the 'grid' variable. I don't understand why it exists. And instead externalized the 'field' variable -> one for each player.
• I merged your two deployPlayerShips() deployComputerShips() methods into one: deployPlayersShips(...). But I still don't understand most of its logic. And with the given code below there are issues at display and field init. But these errors certainly are already present in your original code.
• I have rewritten printBoard() to make use of 'field' variables. But it will still need fixes.
• I fixed partially the playerTurn() and computerTurn() methods as they had badly constructed loops. Turns could never really "turn". The biggest (blocking) problem was in these methods I think (even though other errors remain).
• I've added a global Random() and made Scanner instantiated only once.

package sandbox;

import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;
// ATTENTION: low-quality code based on original source posted in question. Not fully functional and has many issues. But it answers the original question.
public class Warships {
private static final int numRows = 10;
private static final int numCols = 10;
private static final int NB_SHIPS = 5;
private static int playerShips = NB_SHIPS;
private static int computerShips = NB_SHIPS;
private static final int[][] missedGuesses = new int[numRows][numCols];
private static final Random random = new Random(System.currentTimeMillis());
public static final int FIELD_SIZE = 10;
private static final int[][] playerField = new int[FIELD_SIZE][FIELD_SIZE];
private static final int[][] computerField = new int[FIELD_SIZE][FIELD_SIZE];
public static void main(String[] args) {
System.out.println("Welcome to Amiral Batti game");
System.out.println("\nComputer: ");
deployPlayersShips(computerField);
System.out.println("\n");
System.out.println("\nHuman: ");
deployPlayersShips(playerField);
Scanner scn = new Scanner(System.in);  
do {
battle(scn);
} while (playerShips != 0 && computerShips != 0);
gameOver();
}
public static void deployPlayersShips(int[][] field) {       
for (int i = NB_SHIPS; i > 0; i--) {
int x = random.nextInt(field.length);
int y = random.nextInt(field.length);
boolean vertical = random.nextBoolean();
(...)
}    
printBoard2(field);
}
public static void battle(Scanner scn) {                                          
playerTurn(scn);
computerTurn();
System.out.println("\nComputer: ");
printBoard2(computerField);
System.out.println("\nHuman: ");
printBoard2(playerField);
System.out.println();
System.out.println("Your ships: " + playerShips + " | Computer ships: " + computerShips);
System.out.println();
}
public static void playerTurn(Scanner scn) {        
System.out.println("\nHuman's turn: ");
int x = -1, y = -1;
// MAIN ISSUE WAS HERE -- Add correct loop on invalid input
do {
System.out.print("Enter row number: ");
x = scn.nextInt();
System.out.print("Enter column number: ");
y = scn.nextInt();
} while ((x < 0 || x >= numRows) || (y < 0 || y >= numCols));
// MAIN ISSUE WAS HERE -- Removed invalid loop on update field
if (computerField[x][y] != 0 && computerField[x][y] != 9) {
System.out.println("You sunk the ship!");
computerField[x][y] = 1;//"s";
computerShips--;
} else if (".".equals(computerField[x][y])) {
System.out.println("You missed");
computerField[x][y] = 2; //"x";
}                   
}
public static void computerTurn() {
System.out.println("\nComputer's turn: ");
int x = random.nextInt(FIELD_SIZE);
int y = random.nextInt(FIELD_SIZE);
System.out.println("Enter row number: " + x);
System.out.println("Enter column number: " + y);
// MAIN ISSUE WAS HERE -- Removed invalid loop on input/rand
if ((x >= 0 && x < numRows) && (y >= 0 && y < numCols)) {
if (playerField[x][y] != 0 && playerField[x][y] != 9) {
System.out.println("The Computer sunk one of your ships!");
playerField[x][y] = 1;//"s";
playerShips--;
} else if (".".equals(playerField[x][y])) {
System.out.println("Computer missed");
playerField[x][y] = 2; //"x";
if (missedGuesses[x][y] != 1) {
missedGuesses[x][y] = 1;
}
}              
}
}
public static void gameOver() {
System.out.println("Your ships: " + playerShips + " | Computer ships: " + computerShips);
if (playerShips > 0 && computerShips <= 0) {
System.out.println("You won the battle! ");
} else {
System.out.println("You lost the battle! ");
}
System.out.println();
}
public static void printBoard2(int[][] field) {
System.out.print(" ");
System.out.println("0 1 2 3 4 5 6 7 8 9");
char[][] map = new char[FIELD_SIZE][FIELD_SIZE];
for (int i = 0; i < FIELD_SIZE; i++) {
for (int j = 0; j < FIELD_SIZE; j++) {
switch(field[i][j]) {
case 0:
case 9: map[i][j] = '.';
break;
case 1: map[i][j] = 's';
break;
case 2: map[i][j] = 'x';
break;
default: map[i][j] = 'o';
break;
}
}
}
Arrays.stream(map)
.forEach(m -> System.out.println(Arrays.toString(m).replace(",", "")));
}
}

At this point I let you do the rest. Many errors remain. Take the time to truly finish and double-check your code before requesting help again. And keep training there is room for improvements out there in terms of OOP, coding rules and best practices. Good luck.