Below are code examples for reading and writing CSV files using the Java CSV library.

ProductID,ProductName,SupplierID,CategoryID,QuantityPerUnit,UnitPrice,UnitsInStock,UnitsOnOrder,ReorderLevel,Discontinued
1,Chai,1,1,10 boxes x 20 bags,18,39,0,10,FALSE
2,Chang,1,1,24 - 12 oz bottles,19,17,40,25,FALSE
...

import java.io.FileNotFoundException;
import java.io.IOException;

import com.csvreader.CsvReader;

public class CsvReaderExample {

	public static void main(String[] args) {
		try {
			
			CsvReader products = new CsvReader("products.csv");
		
			products.readHeaders();

			while (products.readRecord())
			{
				String productID = products.get("ProductID");
				String productName = products.get("ProductName");
				String supplierID = products.get("SupplierID");
				String categoryID = products.get("CategoryID");
				String quantityPerUnit = products.get("QuantityPerUnit");
				String unitPrice = products.get("UnitPrice");
				String unitsInStock = products.get("UnitsInStock");
				String unitsOnOrder = products.get("UnitsOnOrder");
				String reorderLevel = products.get("ReorderLevel");
				String discontinued = products.get("Discontinued");
				
				// perform program logic here
				System.out.println(productID + ":" + productName);
			}
	
			products.close();
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
	}

}

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import com.csvreader.CsvWriter;

public class CsvWriterAppendExample {
	
	public static void main(String[] args) {
		
		String outputFile = "users.csv";
		
		// before we open the file check to see if it already exists
		boolean alreadyExists = new File(outputFile).exists();
			
		try {
			// use FileWriter constructor that specifies open for appending
			CsvWriter csvOutput = new CsvWriter(new FileWriter(outputFile, true), ',');
			
			// if the file didn't already exist then we need to write out the header line
			if (!alreadyExists)
			{
				csvOutput.write("id");
				csvOutput.write("name");
				csvOutput.endRecord();
			}
			// else assume that the file already has the correct header line
			
			// write out a few records
			csvOutput.write("1");
			csvOutput.write("Bruce");
			csvOutput.endRecord();
			
			csvOutput.write("2");
			csvOutput.write("John");
			csvOutput.endRecord();
			
			csvOutput.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
	}
}

id,name
1,Bruce
2,John