Why do I get this error message: incomparable types: double and nulltype

    Apr 30 2012 | 7:53 am
    I am building a function to interpolate eight lists (it's a 3D interpolation with lists considered as edges of a cube).
    The lists arrive in different inputs and are put in a 2D array. As the lists might have different lengths and the process begins as soon as a list is received, I first seek the length of longest list. Then prior to interpolate I want to check if the eight values do exist (non-null) otherwise I use zeroes. However when I compile I get an error message for this line
    if (items[j][i] == null) {
    The error message is: incomparable types: double and if (items[j][i] == null) {
    The complete function is:
    	public static double interpolate(int numItems, double[] position, double[][] items) {
    		double[] interpolatedValues = new double[numItems];
    		for (int i=0; i
    I don't understand why I get this error message.