interviewprep

Title: Java Part 4

Title: Java

Table of Contents

Sr No.	Question
0	How to clear buffer after processing small portion of the large file?

*. How to clear buffer after processing small portion of the large file (also add CSV to JSON logic)?

To convert a large CSV file to JSON while processing it in small chunks to avoid memory issues, you can follow a similar approach. You’ll read the CSV file line by line, convert each line to a JSON object, and then write the JSON object to a file incrementally.

Here is an example of how you can do this in Java:

import java.io.*;
import org.json.JSONObject;

public class CsvToJsonConverter {

    public static void main(String[] args) {
        String inputFilePath = "path/to/large/input/file.csv";
        String outputFilePath = "path/to/output/file.json";

        convertCsvToJson(inputFilePath, outputFilePath);
    }

    public static void convertCsvToJson(String inputFilePath, String outputFilePath) {
        try (BufferedReader reader = new BufferedReader(new FileReader(inputFilePath));
             BufferedWriter writer = new BufferedWriter(new FileWriter(outputFilePath, true))) { // true for append mode

            String line;
            String[] headers = reader.readLine().split(","); // Assuming first line contains headers

            writer.write("["); // Start of JSON array
            writer.newLine();

            boolean firstLine = true;
            while ((line = reader.readLine()) != null) {
                if (!firstLine) {
                    writer.write(","); // Add a comma between JSON objects
                    writer.newLine();
                }
                String[] values = line.split(",");
                JSONObject jsonObject = new JSONObject();

                for (int i = 0; i < headers.length; i++) {
                    jsonObject.put(headers[i], values[i]);
                }

                writer.write(jsonObject.toString());
                firstLine = false;

                // Flush the writer to clear the buffer
                writer.flush();
            }

            writer.newLine();
            writer.write("]"); // End of JSON array
            writer.newLine();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Key Points:

1. BufferedReader: Used to read the CSV file line by line to avoid loading the entire file into memory.
2. BufferedWriter: Used to write the JSON objects to the output file incrementally in append mode.
3. Flush the Buffer: writer.flush() is called after writing each JSON object to ensure that the buffer is cleared and data is written to the file.
4. JSON Conversion: The org.json.JSONObject class is used to create JSON objects from CSV lines.

This approach ensures that the entire CSV file is not loaded into memory, preventing memory issues while processing large files.