用Java向.csv文件写入数据
如何读取/命名为OpenCSV的库提供了用于从.CSV文件读取数据或将数据写入.CSV文件的API。此处说明了如何使用Java程序读取.csv文件的内容。
Maven依赖
<dependency> <groupId>com.opencsv</groupId> <artifactId>opencsv</artifactId> <version>4.4</version> </dependency> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.9</version> </dependency>
com.opencsv软件包的CSVReader类表示一个简单的csv阅读器。在实例化此类时，您需要将表示要读取的文件的Reader对象作为参数传递给其构造函数。它提供了名为readAll()和readNext()的方法来读取.csv文件的内容
使用readNext()方法
CSVReader类的readNext()方法读取.csv文件的下一行，并以String数组的形式返回。
例
以下Java程序演示了如何使用readNext()方法读取.csv文件的内容。
import java.io.FileReader;
import com.opencsv.CSVReader;
public class ReadFromCSV {
public static void main(String args[]) throws Exception {
//Instantiating the CSVReader class
CSVReader reader = new CSVReader(new FileReader("D://sample.csv"));
//Reading the contents of the csv file
StringBuffer buffer = new StringBuffer();
String line[];
while ((line = reader.readNext()) != null) {
for(int i = 0; i<line.length; i++) {
System.out.print(line[i]+" ");
}
System.out.println(" ");
}
}
}输出结果
id name salary start_date dept 1 Rick 623.3 2012-01-01 IT 2 Dan 515.2 2013-09-23 Operations 3 Michelle 611 2014-11-15 IT 4 Ryan 729 2014-05-11 HR 5 Gary 843.25 2015-03-27 Finance 6 Nina 578 2013-05-21 IT 7 Simon 632.8 2013-07-30 Operations 8 Guru 722.5 2014-06-17 Finance
将数据写入CSV文件
com.opencsv软件包的CSVWriter类表示一个简单的csv编写器。在实例化此类时，您需要传递一个Writer对象作为其构造函数的参数，该对象代表您要向其写入数据的文件。它提供名为writeAll()和writeNext()的方法以将数据写入.csv文件
使用writeNext()方法-
CSVWriter类的writeNext()方法将下一行写入.csv文件
例
以下Java程序演示了如何使用writeNext()方法将数据写入.csv文件。
import java.io.FileWriter;
import com.opencsv.CSVWriter;
public class WritingToCSV {
public static void main(String args[]) throws Exception {
//Instantiating the CSVWriter class
CSVWriter writer = new CSVWriter(new FileWriter("D://output.csv"));
//Writing data to a csv file
String line1[] = {"id", "name", "salary", "start_date", "dept"};
String line2[] = {"1", "Krishna", "2548", "2012-01-01", "IT"};
String line3[] = {"2", "Vishnu", "4522", "2013-02-26", "Operations"};
String line4[] = {"3", "Raja", "3021", "2016-10-10", "HR"};
String line5[] = {"4", "Raghav", "6988", "2012-01-01", "IT"};
//Writing data to the csv file
writer.writeNext(line1);
writer.writeNext(line2);
writer.writeNext(line3);
writer.writeNext(line4);
//Flushing data from writer to file
writer.flush();
System.out.println("Data entered");
}
}输出结果
Data entered