abacus model testing

//I am supposed to make an abacusmodel and test it if it works or not. Now i've made this code,
//but something is not right, the test dosent say whats wrong, so that dosent help.
//Could anyone check the code and see if something obvious is missing?

//workshop 3, until task 4 is what i've done. i now this is a homework but some help would ease my mind,
//because this anoys me. thanks

class AbacusModel 
{
        int num_of_pegs;
        int max_num_counters;
        int peg_array[];

	
	public AbacusModel(int num_pegs, int num_counters)
	{
		max_num_counters = num_counters;
		num_of_pegs = num_pegs;
		peg_array = new int[num_of_pegs];
	}
	
	boolean addCounter(int thisPeg)
   {
 
        if(thisPeg < 0 || thisPeg >= num_of_pegs)
		{
			System.out.println(2);
			return false;
		}		
 
		else if(thisPeg > max_num_counters)
		{
			System.out.println(3);
            return false;
		}
 
		else
		{
			System.out.println(4);
            peg_array[thisPeg]++;
			
            return true;
        }
	}	
		
		
	boolean removeCounter (int thisPeg)
	{
		if(thisPeg < 0 || thisPeg >= num_of_pegs || num_of_pegs < 1 )
		{
			System.out.println(5);
			return false;
		}
		else
		{
			System.out.println(6);
			peg_array[thisPeg]--;
			return true;
		}
			
	}
	
	int getNumCounters(int thisPeg)
	{
		if( thisPeg < 0 || thisPeg > peg_array[thisPeg])
		{
			System.out.println(7);
			return 12;
		}
		
		else
		{
			System.out.println(8);
			return thisPeg;
		}
	}
	
	
		
	
	public static void main(String[] args)
	{
		AbacusModel myAbacus = new AbacusModel(7, 5);

	}
	
	}