My First Java Battleship Simulator (single array, single ship)

Question

I'm new to this community and also to Java programming! I recently picked up "Head First Java" and I did my Battleship project.

If you could kindly, give me feedback on the code?

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

    int location;

    Battleship ship = new Battleship();

    System.out.println("Ship is 3 blocks long, ocean is 10 blocks wide, choose a number: ");

    Scanner scanner = new Scanner(System.in);
    while (ship.end()) {
        location = scanner.nextInt();
        ship.shoot(location);
    }
    System.out.println("Kill!\nYou win!");
}

public static class Battleship {
    private int[] ocean;
    private int shipHead;
    private int counter;

    // check if game is over
    boolean end() {
        if (counter == 3) {
            return false;
        }
        return true;
    }

    // creates the battlefield
    Battleship() {
        ocean = new int[10];
        shipHead = (int) (Math.random() * 7);
        for (int i = shipHead; i < shipHead + 3; i++) {
            ocean[i] = 1;
        }
    }

    // find the start of the ship
    void shipStart() {
        System.out.println("Ship head is at position " + (shipHead + 1));
    }

    // cheat sheet
    void showOcean() {
        for (int i = 0; i < ocean.length; i++) {
            System.out.print(ocean[i] + " ");
        }
        System.out.println();
    }

    void shoot(int a) {
        a -= 1;
        if (a >= 0 && a < 10) {
            switch (ocean[a]) {
                case 1:
                    System.out.println("Hit!");
                    ocean[a] = -1;
                    counter++;
                    break;
                case 0:
                    System.out.println("Miss!");
                    break;
                case -1:
                    System.out.println("Was shot before!");
                    break;
            }
        } else {
            System.out.println("Number between 1 and 10!");
        }
    }

}

}

Answer 1

Your code is clear and clean, I would only suggest:

Opposite name

// check if game is over
boolean end() {
    if (counter == 3) {
        return false;
    }
    return true;
}

I would expect this function to return true when the game ends but it does the opposite, I suggest is_ended as a name and inverting the check, (then use the function with a ! in front). Also the if is not necessary (return counter == 3 is enough).

Separation of concerns

The Battleship class should return Strings rather than printing, the main program should print. This allows easier testing and generalization to Web UI / GUI rather than console only.

Removing magic numbers

    ocean = new int[10];
    shipHead = (int) (Math.random() * 7);
    for (int i = shipHead; i < shipHead + 3; i++) {
        ocean[i] = 1;
    }

What are the numbers 10, 7 and 3? They are respectively boardSize, boardSize - shipSize, shipSize, so boardSize and shipSize should be arguments to the initialization method of Battleship to allow customization of the game to different sizes.

Use an Enum to associate numbers with states

When you write:

 ocean[i] = 1;

It does not mean that there is one thing there while there could be any number of things there, it means SHIP, just as 0 means NOTHING and -1 means DESTROYED. Enums are used when numbers represent concepts rather than quantities. Here is a basic example of enums. Using them will make the code more readable.

Comment for off-by-one errors

Off by one errors are really tricky, so I suggest adding a comment to:

a -= 1;

To:

a -= 1; // User input is 1-index while Java is 0-index