Java:
Working with CSV
How to:
Reading a CSV file using the standard Java library
Java does not have built-in support for CSV in its standard library, but you can easily read a CSV file using java.io
classes.
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ReadCSVExample {
public static void main(String[] args) {
String line;
String csvFile = "data.csv"; // Specify the path to the CSV file
try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {
while ((line = br.readLine()) != null) {
String[] values = line.split(","); // Assuming a comma is the delimiter
// Process the data
for (String value : values) {
System.out.print(value + " ");
}
System.out.println();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Writing to a CSV file using the standard Java library
To write data to a CSV file, you can use java.io
classes such as FileWriter
and BufferedWriter
.
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
public class WriteCSVExample {
public static void main(String[] args) {
String[] data = {"John", "Doe", "30", "New York"};
String csvFile = "output.csv"; // Specify the output CSV file path
try (BufferedWriter bw = new BufferedWriter(new FileWriter(csvFile))) {
StringBuilder sb = new StringBuilder();
for (String value : data) {
sb.append(value).append(","); // Assuming a comma is the delimiter
}
sb.deleteCharAt(sb.length() - 1); // Remove the last comma
bw.write(sb.toString());
bw.newLine();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Using a third-party library: Apache Commons CSV
Apache Commons CSV is a popular library for handling CSV files in Java. It simplifies reading and writing CSV files significantly.
Add the dependency to your project:
For Maven:
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-csv</artifactId>
<version>1.9.0</version> <!-- Check for the latest version -->
</dependency>
Reading a CSV file:
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;
import java.io.Reader;
import java.io.FileReader;
import java.io.IOException;
public class ApacheReadCSVExample {
public static void main(String[] args) {
String csvFile = "data.csv";
try (Reader reader = new FileReader(csvFile);
CSVParser csvParser = new CSVParser(reader, CSVFormat.DEFAULT)) {
for (CSVRecord csvRecord : csvParser) {
// Accessing values by the indexes of columns
String columnOne = csvRecord.get(0);
String columnTwo = csvRecord.get(1);
System.out.println(columnOne + " " + columnTwo);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Writing to a CSV file:
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVPrinter;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
public class ApacheWriteCSVExample {
public static void main(String[] args) {
String[] headers = {"First Name", "Last Name", "Age", "City"};
String[] data = {"John", "Doe", "30", "New York"};
try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.csv"));
CSVPrinter csvPrinter = new CSVPrinter(writer, CSVFormat.DEFAULT.withHeader(headers))) {
csvPrinter.printRecord((Object[]) data); // Casting to Object[] is necessary here
} catch (IOException e) {
e.printStackTrace();
}
}
}
Apache Commons CSV handles complexities such as quotations and commas within fields automatically, making it a robust choice for CSV manipulation in Java.