How to Randomize Multiple ArrayLists While Maintaining Ordering Consistency?

Maintaining Ordering Across Multiple ArrayLists during Randomization

Randomizing a single ArrayList is a straightforward task, but the challenge arises when multiple ArrayLists, related to each other, need to be randomized in a consistent fashion. To achieve this, we can leverage the power of Collections.shuffle() and a shared random seed.

The following code snippet demonstrates how to achieve the desired result:

<code class="java">import java.util.ArrayList;
import java.util.Collections;

public class ArrayListRandomization {

    public static void main(String[] args) {
        // Initialize the ArrayLists
        String[] file = {"H1.txt", "H2.txt", "H3.txt", "M4.txt", "M5.txt", "M6.txt"};
        ArrayList<String> fileList = new ArrayList<>(Arrays.asList(file));

        String[] img = {"e1.jpg", "e2.jpg", "e3.jpg", "e4.jpg", "e5.jpg", "e6.jpg"};
        ArrayList<String> imgList = new ArrayList<>(Arrays.asList(img));

        // Generate a shared random seed
        long seed = System.nanoTime();

        // Randomize the file list
        Collections.shuffle(fileList, new Random(seed));

        // Randomize the image list using the same seed
        Collections.shuffle(imgList, new Random(seed));

        // Print the randomized ArrayLists
        System.out.println("Randomized fileList:");
        for (String s : fileList) {
            System.out.println(s);
        }

        System.out.println("Randomized imgList:");
        for (String s : imgList) {
            System.out.println(s);
        }
    }
}</code>

In this code:

• We obtain a shared random seed using System.nanoTime().
• We use Collections.shuffle() with the shared seed to randomize the fileList.
• We repeat the randomization process for the imgList using the same seed.

By using a shared random seed, both ArrayLists are randomized in the same way, ensuring that the relationship between the corresponding elements is maintained.

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