public class Ragged {

	public static double colAvg (int[][] a, int c) {
		double sum=0;
		int count=0;
		for (int r=0; r<a.length; r++)
			if (a[r] != null)
				if (a[r].length > c) {
					sum+=a[r][c];
					count++;
			}
		return sum/count;
	} // colAvg
	
	public static void display2Darray(int[][] a)  {
		for (int[] row: a) {
    		if (row != null)
    			if (row.length == 0)
    				System.out.print("empty");
    			else
    				for (double d: row)
    					System.out.print(d+"\t");
    		else
    			System.out.print("null");
    		System.out.println();
    	} // for
	} // display2Darray
	
    public static void main(String[] args) {
    	int[][] m = new int[5][];
    	
    	int[] m0 = {2, 5, 7, 9, 6};
    	m[0] = m0;
    	
    	int[] m2 = {8, 6, 4};
    	m[2] = m2;
    	
    	int[] m3 = {15, 25,35, 45, 65, 75, 85};
    	m[3] = m3;
    	
    	int[] m4 = {};
    	m[4] = m4;
    	
    	display2Darray(m);
    	
    	System.out.println("Average of col 0 "+colAvg(m, 0));
    	System.out.println("Average of col 1 "+colAvg(m, 1));
    	System.out.println("Average of col 3 "+colAvg(m, 3));
    	System.out.println("Average of col 5 "+colAvg(m, 5));
    }
    
    
}