Adding elements to a certain part of a 2 dimensional array

Question

So I have to make a battleship map that has 3 different terrains to the map. It has to have sea, land and mountains. I have the sea and land already working. I have to put mountains on only the land terrain but I have no idea how to do that? Thank you for the help. Heres my code:

import java.util.Random;

public class Map {
    protected int numberOfRows; // number of rows in my map
    protected int numberOfColumns; // number of columns in my map
    protected int randomRow;
    protected int randomColumn;

    Terrain terrain [][]; // creates an instance of my terrain

    public Map(int rows, int columns)  { // creates a constructer
        numberOfRows = rows; 
        numberOfColumns = columns;
        terrain = new Terrain[rows][columns]; // puts my number of rows and columns in array
        for(int i = 0; i < rows; i++)  {
            for(int k = 0; k < columns; k++)  {
                terrain[i][k] = new SeaTerrain(); // feels my map with all sea
            }
        }
        addLand(); // runs my add land method
    }

    public void print()  {
        // nested for loop to print my map
        for(int i =0; i < numberOfRows; i++)  {
            for(int j = 0; j < numberOfColumns; j++)  {
                System.out.print(terrain[i][j].getDisplayChar());
            }
            System.out.println("");
        }
    }

    public void addLand()  {
        Random r = new Random();
        int numberOfTimesToRun = r.nextInt(3)+2; // how many islands will be produced
        int temp = 0;
        while(temp <= numberOfTimesToRun)  {
            temp++;

            try { // try catch just incase if the land exceeds my array limit
                randomRow = r.nextInt(40); // picks a random coordinate for my island
                randomColumn = r.nextInt(40); // picks a random coordiante for my island

                int maxRowSize = 20; // max sizes for my islands
                int maxColumnSize = 20;

                int randomColumnSize = r.nextInt(maxColumnSize)+5;
                int randomRowSize = r.nextInt(maxRowSize)+5;

                terrain[randomRow][randomColumn] = new LandTerrain();

                // feels my islands up with the dislay character of "+"
                for(int i = 0; i < randomRowSize; i++)  {
                    terrain[randomRow + i][randomColumn] = new LandTerrain();
                    for(int k = 0; k < randomColumnSize; k++)  {
                        terrain[randomRow+i][randomColumn + k] = new LandTerrain();
                    }
                }

            } catch (Exception e) {

            }
        }
    }
}

//heres my output

    ........................................
    ........................................
    ........................++++++++........
    ........................++++++++........
    ........................++++++++........
    ........................++++++++........
    ........................++++++++........
    ..+++++++++++++++.......++++++++........
    ..+++++++++++++++.......++++++++........
    ..+++++++++++++++.......++++++++........
    ..+++++++++++++++.......++++++++........
    ..+++++++++++++++.......++++++++........
    ..+++++++++++++++.......++++++++........
    ..+++++++++++++++.......++++++++........
    ..+++++++++++++++.......................
    ..+++++++++++++++.......................
    ..+++++++++++++++.......................
    ..+++++++++++++++....++++++++...........
    ..+++++++++++++++....++++++++...........
    ..+++++++++++++++....++++++++...........
    ..+++++++++++++++.......................
    ..+++++++++++++++.......................
    ..+++++++++++++++.......................
    ..+++++++++++++++.......................
    ..+++++++++++++++.......................
    ........................................
    ........................................
    ........................................

So you're asking how you can add mountains on land terrain only? As in on all land-tiles or some land tiles? — PakkuDon
– PakkuDon, Commented Feb 22, 2014 at 2:15
What does your LandTerrain class look like? does it have a method to add mountains? You can loop though the tiles you already added and check if they are LandTerrain using instanceof. — helderdarocha
– helderdarocha, Commented Feb 22, 2014 at 2:17

fersarr · Accepted Answer · 2014-02-22 03:15:03Z

So first you assign water to every piece of map,

second you create random-sized islands on top of the water.

And Now you want to do almost the same thing, add mountains on top of the land (not on top of the water like before)... right?

I have two ideas, the first should be faster

Method 1 Each time you create an island, while you are adding landTerrains, you throw a dice (random.nextInt()) if it's inside some value range, you make that a MountainTerrain instead.

// feels my islands up with the dislay character of "+"
for(int i = 0; i < randomRowSize; i++)  {
    terrain[randomRow + i][randomColumn] = new LandTerrain();
    for(int k = 0; k < randomColumnSize; k++)  {
        if(r.nextInt(10)>8){ //10% probability
            terrain[randomRow+i][randomColumn + k] = new MountainTerrain();

        }
    }
}

Method 2 You should do the same thing as when adding the land but this time every time you are going to add a mountain, just ask if that particular piece of map (or matrix element) is land.

boolean addedMountain=false;
int i = r.nextInt(numberOfRows);
int j = r.nextInt(numberOfColumns);
while(addedMountain==false){
    if(terrain[i][k].getType()=="Land"){ //just to give you an idea
        terrain[i][k] = new MountainTerrain();
        addedMountain=true;
    }
    else{
        //try again?
        i = r.nextInt(limit);
        j = r.nextInt(limit);
    }
}

You would need to do that for each mountain you want to add.

I think a mountain could be just one matrix element, right? But If your mountains need to be blocks (more than one matrix element) you could grow them from that randomly chosen pixel until you hit water.

what if i cant make my mountains just be by themselves. they have to be on land and they cannot be touching the water?

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