Use Apache Commons CSV to implement data conversion and formatting in the Java class library
Use Apache Commons CSV to implement data conversion and formatting in the Java class library
Apache Commons CSV is a Java class library for processing the CSV (comma division value) file.It provides a simple and flexible way to read, write and operate CSV data.This article will introduce how to use Apache Commons CSV to transform and formatize data in the Java class library, and provide corresponding Java code examples.
## Apache Commons CSV Introduction
Apache Commons CSV provides a set of simple and easy -to -use and functional APIs to facilitate handling CSV files.It supports reading CSV data into the Java object to facilitate further operation and processing.At the same time, it also supports the data of the Java object to CSV format to facilitate the export and sharing of data.
## Reading CSV data
The following is a sample code for reading CSV files with Apache Commons CSV:
import org.apache.commons.csv.*;
public class CSVReaderExample {
public static void main(String[] args) throws Exception {
CSVParser parser = CSVParser.parse(new File("data.csv"), Charset.defaultCharset(), CSVFormat.DEFAULT);
for (CSVRecord record : parser) {
String name = record.get(0);
int age = Integer.parseInt(record.get(1));
String email = record.get(2);
// further processing the read data
// ...
}
parser.close();
}
}
In the above example, we read CSV data from a file called "Data.csv" with the `csvparser`.Through the `CSVRecord` object, we can traverse the data in the CSV file one by one and use the` Get` method to obtain the value of each column.You can further process the data you read according to the specific business needs.
## CSV data
The following is an example code written to the CSV file with Apache Commons CSV:
import org.apache.commons.csv.*;
public class CSVWriterExample {
public static void main(String[] args) throws Exception {
CSVPrinter printer = new CSVPrinter(new FileWriter("output.csv"), CSVFormat.DEFAULT);
printer.printRecord("John Doe", 25, "johndoe@example.com");
printer.printRecord("Jane Smith", 30, "janesmith@example.com");
printer.printRecord("Tom Johnson", 35, "tomjohnson@example.com");
printer.close();
}
}
In the above example, we use the `csvprinter` to write the data into a file named" Output.csv ".By calling the `PrintRecord` method multiple times, we can write multi -line data into the CSV file.The parameters of each method of the `PrintRecord` method are the data of each line, which can be a string or other data type.
## Data formatting
In addition to reading and writing CSV data, Apache Commons CSV also provides some data formatting functions.For example, you can set the parser of each column of data (such as the date format), or the conversion process of customized data.
The following is a sample code of data formatting:
import org.apache.commons.csv.*;
public class CSVFormattingExample {
public static void main(String[] args) throws Exception {
CSVParser parser = CSVParser.parse(new File("data.csv"), Charset.defaultCharset(), CSVFormat.DEFAULT.withHeader());
for (CSVRecord record : parser) {
String name = record.get("Name");
int age = Integer.parseInt(record.get("Age"));
String email = record.get("Email");
// Format data
String formattedName = name.toUpperCase();
String formattedEmail = email.toLowerCase();
// further processing the formatted data
// ...
}
parser.close();
}
}
In the above example, we use the `Withheader` method to use the first line of the CSV file as the title.In this way, we can obtain the value of each column through the title instead of indexes.After obtaining the data, we use the `TOUPPERCASE` and` TOLOWERCASE` methods to format the name and email into uppercase and lowercase, respectively.You can format the data according to specific needs.
## Summarize
This article introduces how to use Apache Commons CSV to implement data conversion and formatting in the Java class library.We have discussed how to read and write CSV files with Apache Commons CSV, and demonstrate how to format CSV data.I hope this article can help you better understand and use Apache Commons CSV.
Note: In order to run the example code, make sure you have introduced the relevant dependencies of Apache Commons CSV in the project and prepare the available CSV files.
