使用 OpenCSV
用 Java 编写 CSV 文件
原文:https://www . geesforgeks . org/writing-a-CSV-file-in-Java-using-opencsv/
逗号分隔值(CSV)文件只是一个普通的纯文本文件，逐列存储数据，并用分隔符将其拆分(例如，通常是逗号“，”)。
OpenCSV 是一个面向 Java 的 CSV 解析器库。OpenCSV 支持所有你想做的基本 CSV 类型的操作。Java 7 是目前 OpenCSV 支持的最低版本。Java 语言没有为有效处理 CSV 文件提供任何本机支持，所以我们在 Java 中使用 OpenCSV 来处理 CSV 文件。
如何在项目中添加 OpenCSV？
-
对于 maven 项目，您可以在 pom.xml 文件中包含 OpenCSV maven 依赖项。
java <dependency> <groupId>com.opencsv</groupId> <artifactId>opencsv</artifactId> <version>4.1</version> </dependency>- 对于 Gradle 项目，您可以包含 OpenCSV 依赖项。
java compile group: 'com.opencsv', name: 'opencsv', version: '4.1'- You can Download OpenCSV Jar and include in your project class path.
Writing a CSV File - Write Data Line by line – CSVWriter can write line by line using writeNext() method where a string array is passed with each comma-separated element as a separate entry. CODE:
```java public static void writeDataLineByLine(String filePath) { // first create file object for file placed at location // specified by filepath File file = new File(filePath); try { // create FileWriter object with file as parameter FileWriter outputfile = new FileWriter(file);
// create CSVWriter object filewriter object as parameter CSVWriter writer = new CSVWriter(outputfile);
// adding header to csv String[] header = { "Name", "Class", "Marks" }; writer.writeNext(header);
// add data to csv String[] data1 = { "Aman", "10", "620" }; writer.writeNext(data1); String[] data2 = { "Suraj", "10", "630" }; writer.writeNext(data2);
// closing writer connection writer.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } ```
输出:结果. csv 文件，包含以下数据
```java "Name", "Class", "Marks" "Aman", "10", "620" "Suraj", "10", "630"
```
- Write all Data at once- For witting data at once call writeAll() method of CSVWriter class and pass A List of String[] as the parameter with each String[] representing a line of the file. CODE:
```java public static void writeDataAtOnce(String filePath) {
// first create file object for file placed at location // specified by filepath File file = new File(filePath);
try { // create FileWriter object with file as parameter FileWriter outputfile = new FileWriter(file);
// create CSVWriter object filewriter object as parameter CSVWriter writer = new CSVWriter(outputfile);
// create a List which contains String array List data = new ArrayList(); data.add(new String[] { "Name", "Class", "Marks" }); data.add(new String[] { "Aman", "10", "620" }); data.add(new String[] { "Suraj", "10", "630" }); writer.writeAll(data);
// closing writer connection writer.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } ```
输出:结果. csv 文件，包含以下数据
```java "Name", "Class", "Marks" "Aman", "10", "620" "Suraj", "10", "630"
```
Writing CSV File with different separator By default, the separator for CSV will be a comma(, ). If you want to make another character as a separator so it can be passed as an argument to CSVWriter class.
```java Syntax : CSVWriter(Writer writer, char separator, char quotechar, char escapechar, String lineEnd) Description : Constructs CSVWriter with supplied separator, quote char, escape char and line ending.
```
代码:
```java public static void writeDataForCustomSeparatorCSV(String filePath) {
// first create file object for file placed at location // specified by filepath File file = new File(filePath);
try { // create FileWriter object with file as parameter FileWriter outputfile = new FileWriter(file);
// create CSVWriter with '|' as separator CSVWriter writer = new CSVWriter(outputfile, '|', CSVWriter.NO_QUOTE_CHARACTER, CSVWriter.DEFAULT_ESCAPE_CHARACTER, CSVWriter.DEFAULT_LINE_END);
// create a List which contains String array List data = new ArrayList(); data.add(new String[] { "Name", "Class", "Marks" }); data.add(new String[] { "Aman", "10", "620" }); data.add(new String[] { "Suraj", "10", "630" }); writer.writeAll(data);
// closing writer connection writer.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } ```
输出:结果. csv 文件，包含以下数据
```java Name|Class|Marks Aman|10|620 Suraj|10|630
```
示例: 让我们创建一个 java 程序，它生成一个分号分隔的 csv 文件，并包含作为输入提供的数据。
```java Input: Enter no of rows 9 Enter Data Name Class Marks Aman 10 543 Amar 10 541 Sanjeet 10 555 Luv 10 580 Ranjeet 10 512 Rabi 10 540 Dev 10 333 Sunny 10 198
```
代码:
```java // Java program to illustrate // for Writing Data in CSV file import java.io.; import java.util.; import com.opencsv.CSVWriter;
public class ResultGenerator { private static final String CSV_FILE_PATH = "./result.csv"; public static void main(String[] args) { addDataToCSV(CSV_FILE_PATH); } public static void addDataToCSV(String output) { // first create file object for file placed at location // specified by filepath File file = new File(output); Scanner sc = new Scanner(System.in); try { // create FileWriter object with file as parameter FileWriter outputfile = new FileWriter(file);
// create CSVWriter with ';' as separator CSVWriter writer = new CSVWriter(outputfile, ';', CSVWriter.NO_QUOTE_CHARACTER, CSVWriter.DEFAULT_ESCAPE_CHARACTER, CSVWriter.DEFAULT_LINE_END);
// create a List which contains Data List data = new ArrayList();
System.out.println("Enter no of rows"); int noOfRow = Integer.parseInt(sc.nextLine()); System.out.println("Enter Data"); for (int i = 0; i < noOfRow; i++) { String row = sc.nextLine(); String[] rowdata = row.split(" "); data.add(rowdata); }
writer.writeAll(data);
// closing writer connection writer.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } ```
输出:结果. csv 文件，包含以下数据
```java Name;Class;Marks Aman;10;543 Amar;10;541 Sanjeet;10;555 Luv;10;580 Ranjeet;10;512 Rabi;10;540 Dev;10;333 Sunny;10;198
```
在未来的文章中，我们将包括更多使用 OpenCSV 对 CSV 文件的操作。 参考: OpenCSV 文档CSV writer 类文档
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