public int evenOdd(int[] nums).

This problem is meant to determine whether you know the
difference between a POSITION in an array (list) and
the VALUE of a number at that position in the array.

Given an array of integers,
If the numbers at ALL of the even positions are even AND
if the numbers at ALL of the odd positions are odd, return true.

BUT If you find any exceptions to this, that is:
an EVEN number at an ODD position OR
an ODD number at an EVEN position, return false.

NOTE: You have to use an INDEXED For-Loop:

for (int i = 0; i < nums.length; i=i+1) {
       int n = nums[i];
}

"i" refers to the POSITION of an element in the list, and
"nums[i]" refers to the VALUE of the element at position i.