10+ Apache Poi 使い方 Ideas

Apache POI Getting Started from www.geeksforgeeks.org

Introduction

Apache POI is a powerful Java library that allows developers to read, write, and manipulate Microsoft Office documents, including Excel and Word files. POI stands for Poor Obfuscation Implementation, and it was created by the Apache Software Foundation to provide a better way to work with these popular file formats. In this tutorial, we will explore how to use Apache POI in 2023 and take advantage of its many features and capabilities.

Downloading and Installing Apache POI

Before we can use Apache POI, we need to download and install it. The latest version of Apache POI can be downloaded from the official Apache website. Once you have downloaded the .jar file, you can add it to your Java project's classpath. You can also use a build tool like Maven or Gradle to manage your dependencies and include Apache POI in your project.

Creating a New Workbook

One of the most common tasks when working with Excel files is creating a new workbook. With Apache POI, this is a simple process. We can create a new workbook by instantiating the XSSFWorkbook class:

XSSFWorkbook workbook = new XSSFWorkbook();

This will create a new workbook with a single sheet. We can add more sheets to the workbook by using the createSheet() method:

XSSFSheet sheet = workbook.createSheet("Sheet1");

Reading and Writing Data to Excel Files

Another common task when working with Excel files is reading and writing data. With Apache POI, we can easily read and write data to Excel files. We can write data to a cell by using the setCellValue() method:

XSSFRow row = sheet.createRow(0);
XSSFCell cell = row.createCell(0);
cell.setCellValue("Hello, World!");

We can read data from a cell by using the getCellValue() method:

XSSFCell cell = row.getCell(0);
String value = cell.getStringCellValue();
System.out.println(value);

Formatting Excel Files

Formatting is an important part of creating professional-looking Excel files. With Apache POI, we can format cells, rows, and columns in a variety of ways. We can set the font, font size, font color, and background color of a cell by using the setCellStyle() method:

XSSFCellStyle style = workbook.createCellStyle();
style.setFont(font);
style.setFillForegroundColor(IndexedColors.YELLOW.getIndex());
style.setFillPattern(FillPatternType.SOLID_FOREGROUND);
cell.setCellStyle(style);

Working with Formulas

Excel files often contain formulas that perform calculations and manipulate data. With Apache POI, we can create and manipulate formulas in our Excel files. We can create a formula by using the setCellFormula() method:

XSSFCell cell = row.createCell(1);
cell.setCellFormula("SUM(A1:A10)");

We can also evaluate a formula and get its result by using the evaluateFormulaCell() method:

XSSFCell cell = row.getCell(1);
double value = cell.getNumericCellValue();
System.out.println(value);

Conclusion

Apache POI is a powerful and flexible Java library that makes it easy to work with Microsoft Office documents. In this tutorial, we have covered some of the basics of using Apache POI in 2023, including creating a new workbook, reading and writing data, formatting Excel files, and working with formulas. With these skills, you can create professional-quality Excel and Word files and take your Java programming to the next level.