Скачать или смотреть Mastering Java 8: Converting Loops into Streams and Summing Values with Lambdas

Learn how to transform traditional for loops in Java to the powerful stream and lambda functionalities introduced in Java 8. This guide will help you simplify your code and improve readability while summing values seamlessly!
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The Challenge: Converting Java 8 Loops to Streams

As Java developers transition to newer versions of the language, one common concern arises: how do we convert our traditional loop structures into Java 8’s functional paradigm using streams and lambdas?

You might have a piece of code that loops over collections, applying filtering and summing logic, like the following:

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This code works, but it could be simplified and made more readable by leveraging the power of streams! In this post, we’ll explore how to do just that.

The Solution: Transforming the Code

To convert the above loop to use Java 8 streams and lambdas for functionality, follow these structured steps.

Step 1: Create a Stream from the List

To get started, you need to convert your list into a stream. Streams allow for functional operations like filter, map, and reduce.

Step 2: Use a Matcher with Streams

Instead of directly using the Matcher inside the loop, we can create the Matcher for each string in the stream using a reference to the Pattern:

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Step 3: Filter the Stream

Next, filter the stream to only include elements that match our regex. This is where the find method comes in:

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Step 4: Extract the Desired Data

Once we know which strings matched, we can extract the relevant data using the group method. If you're summing numbers as integers that were matched, it should look like this:

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Step 5: Convert and Sum

Lastly, transform the strings to integers and perform the summation:

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Complete Solution Code

Here’s how the complete Java 8 stream solution looks:

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Or, alternatively, with the use of lambdas:

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Conclusion: Simplifying Code with Streams and Lambdas

Transitioning from traditional loops to Java 8’s stream and lambda expressions may seem daunting initially, but with practice, it becomes a powerful tool for making your code more concise and readable. By breaking down the task into methodical steps—creating a stream, filtering matches, extracting data, and summing—you can take advantage of this modern language feature with ease.

Happy coding!