How to Read a .csv File Into a 2D-array in Java Using Scanner and .split()

Learn how to effectively read a `.csv` file into a `2D-array` in Java using the `Scanner` class and the `.split()` method. This guide covers common mistakes and provides a step-by-step solution.
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This video is based on the question https://stackoverflow.com/q/72531009/ asked by the user '0xCorvo' ( https://stackoverflow.com/u/19284494/ ) and on the answer https://stackoverflow.com/a/72531524/ provided by the user 'Fakhar uddin Malik' ( https://stackoverflow.com/u/6260817/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Read a .csv File Into a 2D-array in Java Using Scanner and .split()

Working with .csv files can sometimes be a bit tricky, especially when you need to read them into a data structure like a 2D-array in Java. If you've found yourself stuck trying to accomplish this task using the Scanner class and the .split() method, you're not alone. This guide will discuss common pitfalls and provide a clear, step-by-step solution to help you successfully load your .csv data into a 2D-array.

The Problem at Hand

Imagine you're working on a homework assignment where you need to read a Sudoku puzzle from a .csv file, which looks like this:

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

Your goal is to read this data into a 2D-array using Java, specifically with the Scanner class and the .split() method. However, you face challenges—your implementation seems to only load the second-to-last line correctly.

Understanding the Solution

Let's dive into the solution with a detailed breakdown:

Setup the Scanner: Before you can read a file, you need to set up what file you're accessing with the Scanner.

Iterate through lines: Rather than using nested loops for the lines and tokens, use a single loop for lines and an inner loop for the tokens.

Populate the 2D-array: Directly assign the parsed integer values to the array in a clear manner.

Here’s an improved version of your original code that corrects the issues:

Correct Code to Read a .csv File

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

Key Changes Explained

Loop Structure: Instead of nesting two loops inside the while loop, we now have just one loop to iterate through the lines of the file while maintaining a separate index for the rows.

Error Handling: The FileNotFoundException is still handled to inform the user if the file cannot be found.

Array Index Management: The row index i is incremented after each line is successfully read and parsed, ensuring data is written to the correct place in the 2D-array.

Conclusion

By following the streamlined approach detailed above, you can easily read .csv files into 2D-arrays in Java using the Scanner and .split() method. This solution not only works efficiently, but it also avoids common pitfalls that can lead to partial data reads. Happy coding!