Скачать или смотреть How to Reduce a Matrix to One Single Element per Cell in Java

Learn how to use Java streams to reduce a matrix to a single element per cell by summing each sub-array's values efficiently.
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This video is based on the question https://stackoverflow.com/q/62765754/ asked by the user 'mks' ( https://stackoverflow.com/u/13724036/ ) and on the answer https://stackoverflow.com/a/62765974/ provided by the user 'WJS' ( https://stackoverflow.com/u/1552534/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Reduce a Matrix to One Single Element per Cell in Java

If you're working with matrices in Java and looking for a way to simplify your data by summarizing it with single-cell outputs, you're in the right place. In this guide, we'll explore how to transform a two-dimensional array (matrix) into a new structure where each row contains only the sum of its elements. Let’s break down the solution step-by-step!

Understanding the Problem

Suppose you have the following matrix defined in Java:

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Your goal is to convert this input into a new matrix that looks like this:

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Here, each row of the new matrix contains the sum of the corresponding row from the original matrix. In simple terms, you want to “reduce” each row to a single value.

The Initial Code

You had a piece of code that almost completed the task but only returns a one-dimensional array. Here’s the code snippet you were working with:

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The Output Issue

Running the above code will produce the output:

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This is close, but we need a two-dimensional array where each element resides in its own array. Let’s refine this!

The Solution

To achieve our desired output format, we need to adjust the code slightly. Here’s the revised solution that transforms the matrix properly:

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Explanation of the Code

Here’s how this code works step-by-step:

Streaming the Matrix: The Arrays.stream(matrix) call streams each of the sub-arrays (or rows) in the matrix.

Summing Elements: For each sub-array, IntStream.of(a).sum() calculates the sum of the elements, effectively reducing the row to a single value.

Wrapping in an Array: We then wrap that sum in a new single-element array new int[]{...}.

Creating a 2D Array: Finally, toArray(int[][]::new) collects all these single-element arrays into a new two-dimensional array.

Final Output

When you run this code, it will print:

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

Just as we wanted! Each row of the output is a separate array containing the sum of the values from each row of the input matrix.

Conclusion

With the help of Java streams, we've effectively transformed a multi-dimensional array into a more manageable format, reducing each row to its sum. This approach is not only concise but leverages the power of streams for efficient data processing.

Now that you have the solution at your fingertips, feel free to adapt this method for other similar matrix operations in your Java projects! Happy coding!