Welcome to another pivotal lesson in your Java interview preparation. In this lesson, we will concentrate on Advanced Array Manipulation Techniques, focusing on the representation and manipulation of arrays directly, without relying on built-in functions. This topic is indispensable when preparing for technical interviews, as many problems often involve performing various operations on arrays.

Take, for example, the Java code provided for rotating an array by k positions. The operation can appear complex initially, but it is made simple by understanding how array indices function. In Java, arrays are fixed in size, and we need to use loops or manual approaches to achieve the desired operations.

In this example, we will manually perform a rotation by k positions using a series of steps to break down and reassemble the array content.

The code might look like this:

Java
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1public class Solution {
2
3    public static void rotateArray(int[] nums, int k) {
4        // Ensure k is within the bounds of the array length
5        k = k % nums.length; 
6        // Reverse the entire array
7        reverse(nums, 0, nums.length - 1);
8        // Reverse the first k elements
9        reverse(nums, 0, k - 1);
10        // Reverse the rest of the array
11        reverse(nums, k, nums.length - 1);
12    }
13
14    private static void reverse(int[] nums, int start, int end) {
15        while (start < end) {
16            int temp = nums[start];
17            nums[start] = nums[end];
18            nums[end] = temp;
19            start++;
20            end--;
21        }
22    }
23
24    public static void main(String[] args) {
25        int[] nums = {1, 2, 3, 4, 5, 6, 7};
26        int k = 3;
27        rotateArray(nums, k);
28        for (int num : nums) {
29            System.out.print(num + " ");
30        }
31        // Output: 5 6 7 1 2 3 4
32    }
33}

In this example, when k = 3, the algorithm first reverses the entire array, resulting in [7, 6, 5, 4, 3, 2, 1]. Then, it reverses the first k elements, giving us [5, 6, 7, 4, 3, 2, 1], and finally, reverses the rest of the array to get [5, 6, 7, 1, 2, 3, 4], achieving the desired rotation.

Developing proficiency in Advanced Array Manipulation Techniques is rewarding and powerful, as it not only opens up efficient ways to solve problems that may appear convoluted at first, but also cultivates the skills necessary for handling even more complex algorithms. Through practice exercises, we aim to equip you with an intuitive understanding of these techniques, which will significantly aid you in your problem-solving abilities. So, let's get started!