Time complexity of tape equilibirum
You inner loop contains:

int differnce = Math.abs(Arrays.stream(array, 0, i).sum() - Arrays.stream(array, i, array.length).sum());


That does (i-0) operations for first sum and (array.length-i) for second, for a total of array.length-i+i-0=array.length. As the size of input is n=array.length that really gives O(n*n). Replacing for-loops with Streams doesn't improve complexity, only hides it a bit.