Pfthb

So I have a class Cup which is part of a game for class. The public int select() method has to return a move in c. I need to generate a random index into c, and I'm told to do this by generating a random number from zero up to and not including the size of the ArrayList. Here's what I have:

import java.util.ArrayList;
import java.util.Random;
public class Cup 

 ArrayList<Integer> c = new ArrayList<Integer>();
 private Random r;

 public Cup() 
 c.add(1);
 c.add(2);
 c.add(3);
 Random r = new Random();
 

 public int count() 
 return c.size();
 

 public int select() 
 int index = r.nextInt(c.size());
 return c.get(index);
 

 public void remove(int m) 
 c.remove(m);
 

When I compile this in the game I'm using, it compiles correctly but tells me there's a Null Pointer exception on the line where r.nextInt(c.size()) is. Just very confusing because I feel like this should be right. Thank you!!!

In your constructor you dont need Random r as you already have a private Random r;

The rest seems to be working. Take care about your remove(int m) method so the user doesn't pass a value greater than the ArrayList's size, to avoid an IndexOutOfBoundsException.

import java.util.ArrayList;
import java.util.Random;

public class Cup 

 ArrayList<Integer> c = new ArrayList<Integer>();
 private Random r;

 public Cup() 
 c.add(1);
 c.add(2);
 c.add(3);

 //here you should use your r attribute
 r = new Random();
 

 public int count() 
 return c.size();
 

 public int select() 
 int index = r.nextInt(c.size());
 return c.get(index);
 

 public void remove(int m) 
 c.remove(m);