How to Merge Two Array Lists in Java, Sort, and Remove Zeroes

Discover how to effectively merge two array lists in Java, sort them, and eliminate zeroes for a clean output.
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Merging Two Array Lists in Java: A Step-by-Step Guide

When you're working with Java, handling collections of data through array lists is a common task. But sometimes, merging two lists, sorting them, and filtering out unwanted values like zeroes can become a bit tricky. If you've found yourself struggling with an issue where you can't seem to merge and sort two array lists correctly, you're not alone! In this guide, we'll explore how you can effectively merge two array lists, remove any zeroes present, and yield a clean, sorted output.

The Problem

Consider this example: you have two array lists where the first list consists of the elements (1, 2, 3, 0, 0, 0) and the second list consists of (2, 5, 6). Your goal is to combine these lists to obtain a merged and sorted result, such as (1, 2, 2, 3, 5, 6). Unfortunately, many Java developers encounter an issue when attempting to print out the results, often ending up with just the elements of the second list.

This confusion can stem from the way elements are accessed and stored during list operations.

Understanding the Code

Let’s take a look at the problematic Java code that you started with:

[[See Video to Reveal this Text or Code Snippet]]

Issues in the Code

Variable Overwriting: The key issue here is that the variable hold is being overwritten in each iteration of the loop. As a result, when you print hold, you are only seeing the most recently assigned value from nums2 and losing the value from nums1 in the process.

The Solution

To ensure you can merge and sort the two array lists effectively while also filtering out the unwanted zero values, let’s refine the code. Here’s an improved version:

[[See Video to Reveal this Text or Code Snippet]]

Key Steps Explained

Create a New List: Start with a new array list named mergedList to hold the combined elements.

Filter out Zeroes: Iterate through nums1 and add only non-zero elements to mergedList.

Merge Lists: Use addAll() to append all elements from nums2 to mergedList.

Print Results: Finally, print mergedList to see the combined and sorted output.

Conclusion

In just a few steps, you can resolve the issue of merging two array lists in Java, sorting them accurately, and removing any unwanted zeroes. Mastering these techniques not only makes your code cleaner and more efficient, but it also equips you with skills to handle complex data manipulation tasks with confidence. Happy coding!