Reading a CSV (Comma Separated Values) file in Java is a common task, especially when dealing with data exchange between different applications. Java provides several ways to read a CSV file, including using the built-in `BufferedReader` class, the `Scanner` class, or third-party libraries like OpenCSV.
Using BufferedReader
One of the simplest ways to read a CSV file in Java is by using the BufferedReader class. This class reads text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ReadCSV {
public static void main(String[] args) {
String csvFile = "path/to/your/file.csv";
String line = "";
String cvsSplitBy = ",";
try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {
while ((line = br.readLine())!= null) {
// use comma as separator
String[] country = line.split(cvsSplitBy);
System.out.println("Country [code=" + country[4] + ", name=" + country[5] + "]");
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Using Scanner
The Scanner class can also be used to read a CSV file. It breaks the input into tokens based on a delimiter, which can be a comma for CSV files.
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class ReadCSV {
public static void main(String[] args) {
String csvFile = "path/to/your/file.csv";
try {
File file = new File(csvFile);
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
String line = scanner.nextLine();
String[] values = line.split(",");
System.out.println("Value 1: " + values[0] + ", Value 2: " + values[1]);
}
scanner.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
Using OpenCSV
OpenCSV is a popular third-party library for reading and writing CSV files in Java. It provides more flexibility and control over the parsing process compared to using BufferedReader or Scanner alone.
import com.opencsv.CSVReader;
import com.opencsv.CSVReaderBuilder;
import java.io.FileReader;
import java.io.IOException;
public class ReadCSV {
public static void main(String[] args) {
String csvFile = "path/to/your/file.csv";
try {
CSVReader csvReader = new CSVReaderBuilder(new FileReader(csvFile))
.withSkipLines(1) // skip header
.build();
String[] nextLine;
while ((nextLine = csvReader.readNext())!= null) {
System.out.println("Name : " + nextLine[0] + ", Age : " + nextLine[1]);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
| Method | Description |
|---|---|
| BufferedReader | Simple, built-in Java class for reading text files line by line. |
| Scanner | Also built-in, it breaks input into tokens based on a delimiter, useful for CSV. |
| OpenCSV | Third-party library offering more features and control over CSV parsing. |
Key Points
- Use `BufferedReader` for simple CSV reading tasks, leveraging its line-by-line reading capability.
- Consider `Scanner` for its token-based approach, which can be handy for CSV files.
- For advanced CSV parsing needs, OpenCSV provides a robust solution with numerous features.
- When choosing a method, consider the size of the CSV file and the specific parsing requirements.
- Always handle potential exceptions, such as `IOException` or `FileNotFoundException`, to ensure robustness.
What is the most efficient way to read a large CSV file in Java?
+For large CSV files, using BufferedReader with a decent buffer size or employing a library like OpenCSV that is optimized for performance can be efficient. However, the best approach depends on the file’s size, the available memory, and the processing requirements.
How do I handle quoted values in a CSV file that contain commas?
+When using BufferedReader or Scanner, handling quoted values that contain commas can be challenging. OpenCSV provides built-in support for quoted values, making it a preferred choice for such scenarios.
Can I use Java 8 Stream API to read a CSV file?
+Yes, Java 8’s Stream API can be used in conjunction with Files.lines() or Files.readAllLines() to read a CSV file, offering a more functional programming approach to parsing CSV files.
