Detailed explanation of Apache Commons CSV framework in the Java class library
Apache Commons CSV is a open source Java class library to process files in Comma-seaPaeth (CSV) format.CSV files are a common text file format, which are usually used in data exchange and storage.
Apache Commons CSV provides a set of simple and powerful APIs that allow developers to read, write and operate CSV files.The following are some of the main characteristics and usage examples of this type of library:
1. Read the CSV file:
Use the `csvparser` class to read the CSV file.It can be implemented by constructing the `CSVPARSER` object and transmitting an` Reader` object.The following is a sample code for reading CSV files:
Reader reader = new FileReader("data.csv");
CSVParser parser = new CSVParser(reader, CSVFormat.DEFAULT);
for (CSVRecord record : parser) {
String name = record.get(0);
int age = Integer.parseInt(record.get(1));
System.out.println("Name: " + name + ", Age: " + age);
}
2. Write into CSV file:
Use the `csvprinter` class to write the CSV file.It can be implemented by constructing the `csvprinter` object and providing an` writer` object.The following is a sample code written to the CSV file:
Writer writer = new FileWriter("data.csv");
CSVPrinter printer = new CSVPrinter(writer, CSVFormat.DEFAULT);
printer.printRecord("John Doe", 25);
printer.printRecord("Jane Smith", 30);
printer.flush();
printer.close();
3. Customized separators and quotes:
Apache Commons CSV supports customizers and quotes characters.You can use the static method of the `csvformat` class to set these options.The following is an example code of a custom separation symbol and quotation:
Reader reader = new FileReader("data.csv");
CSVParser parser = new CSVParser(reader, CSVFormat.newFormat(';').withQuote('"').withHeader());
CSVRecord record = parser.getHeaderMap().get("Name");
System.out.println("Name column index: " + record);
4. Treatment of CSV files with title lines:
If the first line of the CSV file is the title line, you can use the `Withheader` method to specify this information.In this way, you can access the data by indexing.The following is an example code that processs CSV files with a title line:
Reader reader = new FileReader("data.csv");
CSVParser parser = new CSVParser(reader, CSVFormat.DEFAULT.withHeader());
for (CSVRecord record : parser) {
String name = record.get("Name");
int age = Integer.parseInt(record.get("Age"));
System.out.println("Name: " + name + ", Age: " + age);
}
Apache Commons CSV is a powerful and easy -to -use class library that makes it easy to read and write and operate the CSV file.By using this class library, CSV data can be easily processed and integrated with other data sources.Whether it is a large -scale data set or simple data exchange, Apache Commons CSV is a good choice.
