Use the "CSV" framework in the Java class library for data processing
Use the CSV framework in the Java class library for data processing
Overview:
CSV (COMMA-SEPARATED VALUES) is a common file format that is used to exchange data between electronic tables and databases.The CSV framework in the Java class library provides convenient methods to read, write and process CSV files.This article will introduce how to use the CSV framework in the Java library for data processing and provide the corresponding Java code example.
Step 1: Import the CSV framework library
First, you need to import the CSV framework in the Java project.You can obtain the latest version of the CSV framework library from the Maven central warehouse or other reliable resources.
For example, in the Maven project, you can add the following dependencies to the pom.xml file:
<dependency>
<groupId>com.opencsv</groupId>
<artifactId>opencsv</artifactId>
<version>5.5.2</version>
</dependency>
Step 2: Read the CSV file
The CSVReader class is the main class used to read the CSV file in the CSV framework.You can use the instance of CSVReader to read the data in the CSV file row.
The following is a sample code for reading CSV files using CSVReader:
import com.opencsv.CSVReader;
public class CSVReaderExample {
public static void main(String[] args) {
try (CSVReader reader = new CSVReader(new FileReader("example.csv"))) {
String[] line;
while ((line = reader.readNext()) != null) {
for (String value : line) {
System.out.print(value + " ");
}
System.out.println();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
In the above example, we created a CSVReader object and opened a CSV file called "Example.csv".Then, we use the readnext () method to read the data in the CSV file row and store each row of data in a string array.
Step 3: Write into CSV files
The CSVWriter class is the main class used in the CSV framework to write to the CSV file.You can use the CSVWriter instance to write the data into the CSV file.
The following is a sample code written to the CSV file with CSVWriter:
import com.opencsv.CSVWriter;
public class CSVWriterExample {
public static void main(String[] args) {
try (CSVWriter writer = new CSVWriter(new FileWriter("output.csv"))) {
String[] header = {"Name", "Age", "City"};
writer.writeNext(header);
String[] data1 = {"John Doe", "30", "New York"};
writer.writeNext(data1);
String[] data2 = {"Jane Smith", "25", "London"};
writer.writeNext(data2);
} catch (IOException e) {
e.printStackTrace();
}
}
}
In the above example, we created a CSVWriter object and opened a CSV file called "Output.csv".We then use the Writnext () method to write the information such as the header, the data line into the CSV file.
Step 4: Special treatment and custom configuration
The CSV framework also provides some special treatment and custom configuration options to meet different needs.For example, you can specify the configuration of the field separation, quotation character, and lines.
The following is an example code that uses CSVPARSER parser class to customize configuration:
import com.opencsv.CSVReader;
import com.opencsv.CSVParser;
import com.opencsv.CSVParserBuilder;
public class CSVParserExample {
public static void main(String[] args) {
CSVParser parser = new CSVParserBuilder()
.withSeparator(',')
.withQuoteChar('"')
.withEscapeChar('\\')
.build();
try (CSVReader reader = new CSVReader(new FileReader("example.csv"), 0, parser)) {
// Read the CSV file ...
} catch (IOException e) {
e.printStackTrace();
}
}
}
In the above example, we use the CSVPARSERBUILDER class to create a custom configuration CSVPARSER object.In this example, we set the field separation symbols to comma (,), set the quotes character to dual quotation number ("), and set the rigid character to the back slope (\).
in conclusion:
Using the CSV framework in the Java class library can easily handle the reading and writing of the CSV file.You can use the CSVReader class to read the data in the CSV file, and use the CSVWRiter class to write the data into the CSV file.In addition, special processing and custom configuration can be used using the CSVPARSER class.By using the CSV framework, you can handle CSV files more efficiently, and you can set the field separation symbols and quotation characters according to the requirements.
