Efficient CSV Reading & Filtering in Java 📄

Discover how to read a CSV file, filter records by type, and store them in corresponding Java objects using OpenCSV. Learn through practical examples to enhance your coding skills!
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This video is based on the question https://stackoverflow.com/q/68924779/ asked by the user 'krishna' ( https://stackoverflow.com/u/6834055/ ) and on the answer https://stackoverflow.com/a/68925471/ provided by the user 'Timur Efimov' ( https://stackoverflow.com/u/9809131/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Efficiently Read and Filter a CSV File in Java

Working with CSV files is a common task for developers, especially in data-driven applications. However, when the CSV contains mixed types of records—like students and teachers—you may find it challenging to process and filter this data effectively. In this guide, we will explore how to read a CSV file, filter records based on a specific criterion, and store them in different Java objects using the OpenCSV library.

Understanding the CSV Structure

Let's start with the CSV file you need to work with. Here's a snippet of the data you are dealing with:

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This file represents both students and teachers, where the second column identifies the type of record:

S - Student

T - Teacher

The Objective

Your goal is to:

Read the CSV file.

Filter the records: separate student information from teacher information.

Store the data in corresponding Java objects (Student and Teacher classes).

The Solution Using OpenCSV

To achieve this, we'll leverage the OpenCSV library. Below are the steps to filter the records without manually iterating through each line:

1. Define Java Classes for Student and Teacher

First, you need to create two classes to represent the data structure of a student and a teacher.

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

2. Reading and Filtering the CSV

You can read and filter the records based on your criteria while avoiding an inefficient line-by-line approach. Here's how you can do this with OpenCSV:

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

3. Important Notes

The withFilter method allows you to specify a condition to filter CSV records, making the process efficient.

Ensure that you are using the correct column index when binding your fields with @ CsvBindByPosition. For example, the second column (position = 1) will always be 'S' for the Student class.

Unfortunately, as per current OpenCSV capabilities, you cannot set different type mappings within a single builder. Therefore, you will need to handle teacher records separately if you wish to extract them as well.

Conclusion

In conclusion, by using OpenCSV, you can efficiently read and filter records in a CSV file without compromising performance, even when dealing with large datasets. The use of CsvToBeanBuilder and its filter capabilities allows you to separate and manage different record types seamlessly. Start implementing this technique in your projects and see how it simplifies your data handling tasks!

If you have any questions or need further clarification, feel free to reach out in the comments below!