The CSV expansion method media commonly used in the Java class library
CSV (comma segmental value) is a common file format that is used to store and transmit data in form form.In the Java library, there are many commonly used CSV extensions that can help developers read, write and process CSV files more conveniently.The following will introduce several commonly used CSV extensions and provide the corresponding Java code example.
1. Read CSV file data
Reading CSV files is one of the common tasks of processing CSV data.The CSV extension method in the Java class library can help us read data easily from the CSV file and convert it to the Java object.
import com.opencsv.CSVReader;
public class CsvReaderExample {
public static void main(String[] args) {
try (CSVReader reader = new CSVReader(new FileReader("data.csv"))) {
String[] nextLine;
while ((nextLine = reader.readNext()) != null) {
// Process each line of data
for (String cell : nextLine) {
System.out.print(cell + "\t");
}
System.out.println();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
The above code uses the CSVReader class in the OpenCSV library. This class provides the Readnext () method to read the CSV file data row.Each line of data read is returned in the form of a string array, and developers can further process them according to the needs.
2. Write into CSV file data
In addition to reading CSV files, we sometimes need to write data into CSV files.The CSV expansion method in the Java class library provides convenient methods to achieve this function.
import com.opencsv.CSVWriter;
public class CsvWriterExample {
public static void main(String[] args) {
try (CSVWriter writer = new CSVWriter(new FileWriter("data.csv"))) {
String[] record1 = {"John", "Doe", "25"};
String[] record2 = {"Jane", "Smith", "30"};
writer.writeNext(record1);
writer.writeNext(record2);
} catch (IOException e) {
e.printStackTrace();
}
}
}
The above code uses the CSVWriter class in the OpenCSV library. By constructing the CSVWriter object and transmitting the file output stream, we can use the Writnext () method to write the data into the CSV file.Each string array represents a line of data of the CSV file, and each element of the array corresponds to a column.
3. Analyze the CSV data type
Sometimes, we need to convert the string data in the CSV file into the corresponding Java data type.The CSV expansion method in the Java class library can help us easily analyze the CSV data type.
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;
public class CsvParserExample {
public static void main(String[] args) {
try (CSVParser parser = CSVParser.parse(new FileReader("data.csv"), CSVFormat.DEFAULT)) {
for (CSVRecord record : parser) {
String name = record.get(0);
int age = Integer.parseInt(record.get(1));
double salary = Double.parseDouble(record.get(2));
// further processing the data after the analysis
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
The above code uses the CSVPARSER class in the Apache Commons CSV library. By constructing the CSVPARSER object and passing into the file input stream, we can use the get () method to obtain the value of the specific columns in each line.When parsing the data type, we use Integer.PARSEINT () and Double.PARSEDOUBLE () methods to convert the string to integer and floating -point type.
Summarize:
The above introduces the CSV extension method commonly used in the Java library, and provides the corresponding Java code example.These methods can help developers read, write and process data in CSV files more easily.Whether it is reading a lot of data or writing complex data, it can be implemented through the Java class library.I hope these example code can help you!
