Load CSV Data into Map in Java 📊

Discover how to effectively load CSV data into a `Map` structure in Java, using classes and streams, with an example implementation.
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This video is based on the question https://stackoverflow.com/q/62351026/ asked by the user 'here_to_learn' ( https://stackoverflow.com/u/8930064/ ) and on the answer https://stackoverflow.com/a/62352903/ provided by the user 'Eritrean' ( https://stackoverflow.com/u/5176992/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Loading CSV Data into a Map Structure in Java: A Step-by-Step Guide

When working with large datasets, it’s common to need a way to quickly and efficiently process and access the data. One format that many developers encounter is CSV (Comma-Separated Values), particularly in educational settings where student grades are recorded. In this guide, we will explore how to load CSV data into a Map structure in Java. We’ll break it down step-by-step to ensure clarity and understanding.

Understanding the Problem

Consider we have a CSV file representing student scores in various subjects over multiple years. Here's a snapshot of how the data looks:

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The aim is to construct a Map where:

The key is a combination of student name and year (utilized as a Tuple object).

The value is a list of subject scores represented as a SubjectScore object.

This structure allows quick lookups to retrieve subjects and scores based on the student’s name and year.

Defining Data Classes

To achieve this, we need two classes: Tuple for the keys and SubjectScore for the values. Let's review the structure for both.

Tuple Class

This class will store the student’s name and the year. We need to ensure it has correctly implemented equals and hashCode methods to properly function as a key in the map.

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SubjectScore Class

Now for the SubjectScore, we'll define it to capture the subjects and their respective scores.

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

Loading the CSV into a Map

We will now work on reading the CSV file and loading it into our Map<Tuple, List<SubjectScore>>. Below is a comprehensive example of the implementation using Java Streams.

Full Example Implementation

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

Conclusion

Loading CSV data into a Map in Java using the right classes allows for efficient data manipulation and retrieval. The example outlined above helps create a structured and organized codebase that centralizes subject scores by student name and year, simplifying lookups significantly.

Now, give it a try with your own CSV file and see how efficiently you can access student scores based on their name and year!