`nums[nums.length - 1]; ` is an range or single element?

Alice :

I read such a solution to rotate an array

the question:

public class Solution {
    public void rotate(int[] nums, int k) {
        int temp, previous;
        for (int i = 0; i < k; i++) {
            previous = nums[nums.length - 1];
            for (int j = 0; j < nums.length; j++) {
                temp = nums[j];
                nums[j] = previous;
                previous = temp;
            }
        }
    }
}

I am confused about previous = nums[num.lengh -1],
is it a range as nums[0:10] or a single element as nums[0]?

deHaar :

It is a single element, because num.lengh - 1 is an int and just gives you the last accessible index of the array.

If you check wether the length of the array is > 0, then you can safely use the length of the array to determine the last accessible index.

The length of an array is very often used in loops like yours:

Here the length is used to make sure you don't access unavailable indexes:

for (int j = 0; j < nums.length; j++)

You can write slightly a different condition without changing the functionality

for (int j = 0; j <= nums.length - 1; j++)

But if you do the following, you will get an IndexOutOfBoundsException:

for (int j = 0; j <= nums.length; j++) 

The last iteration would try to access nums[nums.length], which isn't there...