Introduced Null Pointer Exception at lambda function, sorts two array

src/sort/MergeSort.java

@@ -10,21 +10,22 @@ public class MergeSort{
 		GeneralCompare b1;
 		b1 = (a1, a2) -> (Integer) a1 - (Integer) a2;
 		Integer[] test = {3, 4, 2, 1, 5, 7, 9, 10};
-		sort(test, 0, Array.getLength(test) - 1, b1);
+		//Integer[] test = {2, 1};
+		sort(test, 0, test.length - 1, b1);
 		
-		for (int i = 0 ; i < (Array.getLength(test) - 1) ; i++) {
+		for (int i = 0 ; i < (test.length) ; i++) {
 			System.out.println(test[i]);
 		}
 	}
 
 	public static void sort(Comparable[] x, int lo, int hi, GeneralCompare gc) {
-		aux = new Comparable[Array.getLength(x)];
-		sortWrapped(x, 0, Array.getLength(x) - 1, gc);
+		aux = new Comparable[x.length];
+		sortWrapped(x, lo, hi, gc);
 	}
 	
 	private static void sortWrapped(Comparable[] x, int lo, int hi, GeneralCompare gc) {
 		int n = hi - lo; 
-		if(n <= 1)
+		if(n < 1)
 			return;
 		// Recursively sort each half of the array
 		int mid = lo + (n/2);
@@ -39,19 +40,36 @@ public class MergeSort{
 		int mid = lo + (n/2);
 
 		// Fill auxiliary array
-		System.out.println(n);
+		System.out.println("lo, mid, hi: " + lo + ", " + mid + ", " + hi);
+		
 		for(int k = lo; k <= hi; k++){
 			aux[k] = x[k];
 		}
 
+		int i = lo; 
+		int j = mid + 1; 
+		for (int k = 0 ; k <= hi ;) {
+			if (i > mid)
+				x[k++] = aux[j++]; //All elems in first half already added to x
+			else if (j > hi)
+				x[k++] = aux[i++]; //All elems in second half already added to x
+			else if (gc.compare(aux[i], aux[j]) > 0)
+				x[k++] = aux[j++]; 
+			else
+				x[k++] = aux[i++];
+		}
+		
+		/*
 		int i = 0;
 		// Merging two sorted arrays
-		while ((lo <= mid) & (mid <= hi)) {
+		while (i <= n) {
 			if (gc.compare(aux[lo], aux[mid]) > 0)
 				x[i++] = aux[mid++]; 
 			else
 				x[i++] = aux[lo++];
 		}
+		*/
+
 
 		/*
 		// Is this portion sorting the aux array? Check