problem with a nullPointerException

static void displayData (String[] input)
	{
		int limit = 10;
		int[] word = new int[limit];
		for (String a: input)
		{
			int b = a.length();
			word[b]++;
		}
		
		for (int i = 0; i< limit;i++)
			System.out.println("There are "+ word[i] + " words with "+ i+ " characters");
		
	}// end display data method