The use of the CSV extension framework in the Java class library
CSV (comma separation value) is a commonly used data storage format that stored data records in the form of commas.In the Java library, many CSV extension frameworks can be used to read, write and operate CSV files.This article will introduce some common CSV expansion frameworks and their usage in Java.
1. OpenCSV
OpenCSV is a popular Java CSV library that provides the function of reading and writing to CSV files.Using OpenCSV, we can easily convert the CSV file into a Java object and convert the Java object to a CSV file.
First, we need to add the OpenCSV library to the project through Maven or Gradle.Then, we can use the following code examples to read and write to the CSV file:
1. Read the CSV file:
import com.opencsv.CSVReader;
import java.io.FileReader;
import java.io.IOException;
public class CsvReaderExample {
public static void main(String[] args) {
try (CSVReader reader = new CSVReader(new FileReader("data.csv"))) {
String[] line;
while ((line = reader.readNext()) != null) {
// Process each row of data
for (String value : line) {
System.out.print(value + ", ");
}
System.out.println();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
2. Write into CSV file:
import com.opencsv.CSVWriter;
import java.io.FileWriter;
import java.io.IOException;
public class CsvWriterExample {
public static void main(String[] args) {
try (CSVWriter writer = new CSVWriter(new FileWriter("data.csv"))) {
String[] header = {"Name", "Age", "City"};
writer.writeNext(header);
// Write into the data line
String[] dataRow1 = {"John Doe", "30", "New York"};
String[] dataRow2 = {"Jane Smith", "25", "Los Angeles"};
writer.writeNext(dataRow1);
writer.writeNext(dataRow2);
} catch (IOException e) {
e.printStackTrace();
}
}
}
2. Apache Commons CSV
Apache Commons CSV is another popular Java CSV library that provides flexible CSV read and write functions.Compared with OpenCSV, Apache Commons CSV provides more options and configurations.
Similarly, we first need to add Apache Commons CSV libraries to the project, and then we can use the following code examples to read and write to the CSV file:
1. Read the CSV file:
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
public class CsvReaderExample {
public static void main(String[] args) {
try (Reader reader = new FileReader("data.csv");
CSVParser csvParser = new CSVParser(reader, CSVFormat.DEFAULT)) {
for (CSVRecord csvRecord : csvParser) {
// Process each row of data
for (String value : csvRecord) {
System.out.print(value + ", ");
}
System.out.println();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
2. Write into CSV file:
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVPrinter;
import java.io.FileWriter;
import java.io.IOException;
public class CsvWriterExample {
public static void main(String[] args) {
try (FileWriter writer = new FileWriter("data.csv");
CSVPrinter csvPrinter = new CSVPrinter(writer, CSVFormat.DEFAULT)) {
csvPrinter.printRecord("Name", "Age", "City");
// Write into the data line
csvPrinter.printRecord("John Doe", "30", "New York");
csvPrinter.printRecord("Jane Smith", "25", "Los Angeles");
} catch (IOException e) {
e.printStackTrace();
}
}
}
The above are examples of the two popular CSV extensions, which use OpenCSV and Apache Commons CSV to read and write CSV files in Java.Whether reading large CSV files or writing complex CSV files, these libraries provide many flexible options and functions to meet various needs.I hope this article can help you understand and use the CSV expansion framework in Java.
