Скачать или смотреть Efficiently Join Two Lists in Java 8 Using Streams

Learn how to combine two lists in Java 8, ensuring that elements at the same index are joined together in a clean format. Find out how to achieve this using functional programming concepts.
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This video is based on the question https://stackoverflow.com/q/62675307/ asked by the user 'Akash Sharma' ( https://stackoverflow.com/u/12426044/ ) and on the answer https://stackoverflow.com/a/62675533/ provided by the user 'Andronicus' ( https://stackoverflow.com/u/7606764/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Join Two Lists in Java 8: A Guide to Combining Elements Effortlessly

Combining lists in Java can be a mundane task, especially when you want to ensure that elements at the same index from two lists come together seamlessly in a resultant string. In this guide, we’ll tackle a specific problem: you have two lists, one containing codes and the other containing names, and you want to join these lists in a way that produces a formatted string. Let's dive into the details of this process using Java 8 features.

The Problem

Suppose you are working with two lists in Java:

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You want to create a resultant string that looks like this:

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This means that for each index of the two lists, you want to combine the elements using a specific format and separate them with a pipe (|). The challenge arises when trying to achieve this directly using Java 8 features without cumbersome loops or manual indexing.

The Solution

The elegance of Java 8 allows us to solve this problem using the IntStream class, which provides a simple solution to index the list elements. Below are the steps and the actual code that accomplishes this task.

Step 1: Import the Necessary Classes

Before we can start coding, ensure you have imported the necessary Java classes:

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Step 2: Prepare the Lists

Make sure you have your lists ready for processing:

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Step 3: Use IntStream to Combine the Lists

Now, let’s leverage IntStream to iterate over the indices and combine the elements. Here’s how you can do it:

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IntStream.range(0, codeList.size()): Generates a stream of indices from 0 to the size of codeList.

mapToObj(i -> codeList.get(i) + "{" + nameList.get(i) + "}"): For each index, retrieves the corresponding elements from both lists and formats them according to our requirements.

collect(Collectors.joining(" | ")): Finally, this concatenates all the formatted strings, separated by a pipe.

Step 4: Output the Result

You can easily print the resultant string:

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Conclusion

Through the power of Java 8’s stream capabilities, we have successfully merged two lists based on their indices, creating a formatted string that meets our needs. This approach not only simplifies the task but also enhances code readability and maintainability.

Feel free to implement this method in your projects and experience the efficiency of functional programming in Java!