Apache POI 是用Java编写的免费开源的跨平台的 Java API，Apache POI提供API给Java程式对Microsoft Office格式档案读和写的功能。该篇是介绍poi基本的读写数据功能。

本文操作的是xls格式的Excel，使用的jar包是：

<dependency>

	<groupId>org.apache.poi</groupId>

	<artifactId>poi</artifactId>

	<version>3.16</version>

</dependency>

如果操作的是xlsx格式的Excel，引入该jar包：

<dependency>

    <groupId>org.apache.poi</groupId>

    <artifactId>poi-ooxml</artifactId>

    <version>xxx</version>

</dependency>

• 数据写入Excel

package com.originexcel;

import org.apache.poi.ss.usermodel.Cell;

import org.apache.poi.xssf.usermodel.XSSFRow;

import org.apache.poi.xssf.usermodel.XSSFSheet;

import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.util.Map;

import java.util.Set;

import java.util.TreeMap;

/**

 * Created by dell on 2017/9/29.

 */

public class CreateSheet {

    public static void main(String[] args) throws IOException {

        /**

         * 思路:

         * 1、创建工作簿

         * 2、创建sheet页(可设置sheet页名)

         * 3、创建行

         * 4、取数据：先取集合，再取对象，再取属性，并将数据写入到工作簿

         * 5、创建文件，将工作簿写入文件

         */

        XSSFWorkbook workbook = new XSSFWorkbook();  // 创建工作簿

        XSSFSheet sheet = workbook.createSheet("mysheet");// sheet页名称

        XSSFRow row ;  // 行

        Map<String,Object[]> object = new TreeMap<>();

        object.put("1",new Object[]{"name","age","sex"});

        object.put("2",new Object[]{"admin01","15","女"});

        object.put("3",new Object[]{"admin02","15","女"});

        object.put("4",new Object[]{"admin03","15","女"});

        object.put("5",new Object[]{"admin04","15","女"});

        object.put("6",new Object[]{"admin05","15","女"});

        Set<String> keys = object.keySet();

        int rowid = 0;

        for (String key:keys) {

            row = sheet.createRow(rowid++);

            Object[] objects = object.get(key);

            int cellid = 0;

            for (Object obj : objects) {

                Cell cell = row.createCell(cellid++);  // 单元格

                cell.setCellValue((String)obj);

            }

        }

        FileOutputStream outputStream = new FileOutputStream(new File("test.xls"));

        workbook.write(outputStream);

        outputStream.close();

        System.out.println("test.xlsx written successfully");

    }

}

输出的效果是：

• 读取excel数据

package com.originexcel;

import org.apache.poi.ss.usermodel.Cell;

import org.apache.poi.ss.usermodel.Row;

import org.apache.poi.xssf.usermodel.XSSFRow;

import org.apache.poi.xssf.usermodel.XSSFSheet;

import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.FileInputStream;

import java.io.IOException;

import java.util.Iterator;

/**

 * 读取excel的数据

 *

 * Created by dell on 2017/9/29.

 */

public class ReadWorkBook {

    static XSSFRow row;

    public static void main(String[] args) throws IOException {

        FileInputStream inputStream = new FileInputStream("test.xls");

        XSSFWorkbook workbook = new XSSFWorkbook(inputStream);

        XSSFSheet sheet = workbook.getSheetAt(0);

        Iterator<Row> rows = sheet.iterator();

        while (rows.hasNext()){

            row = (XSSFRow) rows.next();

            Iterator <Cell> cellIterator = row.cellIterator();

            Cell cell = cellIterator.next();

            switch (cell.getCellType()){

                case Cell.CELL_TYPE_NUMERIC:

                    System.out.print(cell.getNumericCellValue() + " \t\t " );

                    break;

                case Cell.CELL_TYPE_STRING:

                    System.out.print(cell.getStringCellValue() + " \t\t " );

                    break;

            }

            System.out.println();

        }

        inputStream.close();

    }

}

本文只是作为poi一个入门的demo（也是博主的处女作）。欢迎大家多多指教。