Trying to create Battleship game with arraylist

[vamsi naki]

Hi,
I am trying to create a battleship game using arraylist .
The program was meant to first ask how many cells the user wants in the game,then it itself creates coordinates of three ships and ask user input for hitting the ship.
The problem is when i run the code and i wrote a loop to check the co-ordinates of the randomly generated co-ordinates i am getting all co-ordinates as 0,0 for all the ships.

package battleshipgame;
import java.util.*;
import java.io.*;
public class game {

	public static void main(String[] args) {
	game g=new game();
	g.setupgame();
	//g.startgame();
	int []locationcells=new int[3];
	
	}
	

	public void setupgame() 
	{   
		ArrayList<String> ship=new ArrayList<String>();
	    ArrayList<Integer> horizontallocation=new ArrayList<Integer>();
		ArrayList<Integer> verticallocation=new ArrayList<Integer>();
        
        ship.add("one");
		ship.add("two");
		ship.add("three");
		
		System.out.println("how many cells do you want in your game");
		int a=getuserinput();
		a++;
		
		
		for(int i=0;i<ship.size();i++)
		{
		
		 
		if(ship.size()%2==0)
		  {
		    for(int h=0;h<3;h++)
		    {
		    int s=(int)Math.random()*a;
		 	int p=(int)Math.random()*a;	
		 	  if(s!=a)
		 	  {
			  horizontallocation.add(s);
		      verticallocation.add(p);
		      s++;
		      }
		    }   
		  }
		else {
			for(int j=0;j<3;j++)
			{
			  int s=(int)Math.random()*a;
		 	  int p=(int)Math.random()*a;	
		 	  if(p!=a)
		 	   {
			   horizontallocation.add(s);
		       verticallocation.add(p);
		       p++;
		       }
			}
		}
		
		}
		System.out.println("game set up complete");
	
	//public void startgame()
	//{
		for(int m=horizontallocation.size()-1;m>0;m--)
		{
			System.out.println("the horizontal coordinates of the ship are");
			System.out.println(horizontallocation.get(m));
		}
		for(int n= verticallocation.size()-1;n>0;n--)
		{
			System.out.println("the vertical coordinates of the ship are");
			System.out.println(verticallocation.get(n));
		}
		
	    int h;
		int v;
		System.out.println("starting the game");
		System.out.println("hit a cell horizontal location first ,followed by vertical location");
		
		while(!ship.isEmpty())
		{
			h=getuserinput();
			v=getuserinput();
		 if(horizontallocation.contains(h)&&verticallocation.contains(v))
		 {    
			 System.out.println("hit");
			 horizontallocation.remove(h);
			 verticallocation.remove(v);
			 if(horizontallocation.contains(null)&&verticallocation.contains(null))
			 {
				 System.out.println("all ships have been sunk");
			 }
			 
		 }
		 else
		 {
			 System.out.println("miss");
		 }
		}
	}
//}
	public int getuserinput()
	{
		int a=0;
		try{
		BufferedReader myreader=new BufferedReader(new InputStreamReader(System.in));
		a=Integer.parseInt(myreader.readLine());
		}
		catch (IOException i)
		{
			System.out.println("Unable to read user input");
			i.printStackTrace();
			
		}
		
		return a;
	}
	
}

[Greg Brannon]

Since the coordinates are set according to the values s and p, you should investigate what these expressions are evaluating to:

(int)Math.random()*a

[Anayonkar Shivalkar]

Hello vamsi naki,

Welcome to CodeRanch!

i am getting all co-ordinates as 0,0 for all the ships

This is because, when you 'randomly' generate co-ordinate, you are making all of them to 0.

Hint 1 : Math.random returns a random number between 0.0 and 1.0
Hint 2 : What do you get when you cast, say, 0.4 to 'int'?

I hope this helps.

[Darryl Burke]

vamsi naki wrote:The problem is when i run the code and i wrote a loop to check the co-ordinates of the randomly generated co-ordinates i am getting all co-ordinates as 0,0 for all the ships.

int s=(int)Math.random()*a;

From the documentation, Math.random() returns a double greater than or equal to 0.0 and less than 1.0. Casting that to int results in ...?

Aside, why aren't you using the newer java.util.Random?

[Winston Gutkowski]

vamsi naki wrote:i am getting all co-ordinates as 0,0 for all the ships.

I think everybody else has covered the why, but (and this is a general tip) if you want random numbers, you're far better off to use the java.util.Random class.

Why?
1. Because it was written specifically to produce random numbers. Math.random() is just one method in a collection of maths utilities.
2. It's Thread-safe.
3. Math.random() actually uses java.util.Random (as of Java 1.4, I think), so you have the overhead of an additional call.

And the method that you probably need to look at is Random.nextInt(int).

Winston

[Campbell Ritchie]

Winston Gutkowski wrote: . . . Random.nextInt(int).

Winston

That sounds promising. But remember myRandom.nextInt(10) will never give you 10 as a result. Read its documentation.

[Campbell Ritchie]

Actually, the documentation isn’t easy to read. If you pass 10 to that method, you get results between 0 and 9.

[vamsi naki]

Thnaks all for the help ,Darryll i didnt know that there was java.util.Random .I will check it out now.