java.lang.NullPointerException when accessing inner class field
===

I am getting a null pointer exception from the code below at line 19,"seq[index].value = lo;". The sequence class has a value field with integer type, but I think the problem is to access the array of seq instance. Can you please help?



public class ImprovedFibonacci {
	
	class Sequence{
		int value = 0;
		boolean isEven = false;
	}
	
	public static void main(String[] args){
		
		final int MAX_LOOP = 20;
		int lo = 1;
		int hi = 1;
		int i = 0;
		String mark = "-";
		
		int index = 0;
		ImprovedFibonacci.Sequence[] seq = new ImprovedFibonacci.Sequence[MAX_LOOP];
		seq[index].value = lo;
		
		System.out.println("Fibonacci seq 1 : " + lo);
		System.out.println("Sequence class index: "+index+"value: "+seq[index].value);
		
		for(i=MAX_LOOP;i>=1;i--) {
			hi = hi + lo;
			lo = hi - lo;
			index++;
		    if(hi % 2 == 0){
				mark = "-";
				seq[index].isEven = true;
		    }else{
		    	mark = "";
		    }
		    
		    System.out.println(i + " : " + hi + mark);
		    seq[index].value = hi;
		    System.out.println("Sequence class index: "+index+"value: "+seq[index].value+"IsEven: "+seq[index].isEven);
		}
	}
}
