zoukankan      html  css  js  c++  java
  • Apache POI – Reading and Writing Excel file in Java

    来源于:https://www.mkyong.com/java/apache-poi-reading-and-writing-excel-file-in-java/

    In this article, we will discuss about how to read and write an excel file using Apache POI

    1. Basic definitions for Apache POI library

    This section briefly describe about basic classes used during Excel Read and Write.

    1. HSSF is prefixed before the class name to indicate operations related to a Microsoft Excel 2003 file.
    2. XSSF is prefixed before the class name to indicate operations related to a Microsoft Excel 2007 file or later.
    3. XSSFWorkbook and HSSFWorkbook are classes which act as an Excel Workbook
    4. HSSFSheet and XSSFSheet are classes which act as an Excel Worksheet
    5. Row defines an Excel row
    6. Cell defines an Excel cell addressed in reference to a row.

    2. Download Apache POI

    Apache POI library is easily available using Maven Dependencies.

    pom.xml
    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml</artifactId>
      <version>3.15</version>
    </dependency>

    3. Apache POI library – Writing a Simple Excel

    The below code shows how to write a simple Excel file using Apache POI libraries. The code uses a 2 dimensional data array to hold the data. The data is written to a XSSFWorkbook object. XSSFSheet is the work sheet being worked on. The code is as shown below:

    ApachePOIExcelWrite.java
    package com.mkyong;
    
    import org.apache.poi.ss.usermodel.Cell;
    import org.apache.poi.ss.usermodel.Row;
    import org.apache.poi.xssf.usermodel.XSSFSheet;
    import org.apache.poi.xssf.usermodel.XSSFWorkbook;
    
    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import java.io.IOException;
    
    public class ApachePOIExcelWrite {
    
        private static final String FILE_NAME = "/tmp/MyFirstExcel.xlsx";
    
        public static void main(String[] args) {
    
            XSSFWorkbook workbook = new XSSFWorkbook();
            XSSFSheet sheet = workbook.createSheet("Datatypes in Java");
            Object[][] datatypes = {
                    {"Datatype", "Type", "Size(in bytes)"},
                    {"int", "Primitive", 2},
                    {"float", "Primitive", 4},
                    {"double", "Primitive", 8},
                    {"char", "Primitive", 1},
                    {"String", "Non-Primitive", "No fixed size"}
            };
    
            int rowNum = 0;
            System.out.println("Creating excel");
    
            for (Object[] datatype : datatypes) {
                Row row = sheet.createRow(rowNum++);
                int colNum = 0;
                for (Object field : datatype) {
                    Cell cell = row.createCell(colNum++);
                    if (field instanceof String) {
                        cell.setCellValue((String) field);
                    } else if (field instanceof Integer) {
                        cell.setCellValue((Integer) field);
                    }
                }
            }
    
            try {
                FileOutputStream outputStream = new FileOutputStream(FILE_NAME);
                workbook.write(outputStream);
                workbook.close();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
    
            System.out.println("Done");
        }
    }

    On executing the above code, you get below excel as an output.

    apache-poi-read-write-excel

    4. Apache POI library – Reading an Excel file

    The below code explains how to read an Excel file using Apache POI libraries. The function getCellTypeEnum is deprecated in version 3.15 and will be renamed to getCellType from version 4.0 onwards.

    ApachePOIExcelRead.java
    package com.mkyong;
    
    import org.apache.poi.ss.usermodel.*;
    import org.apache.poi.xssf.usermodel.XSSFWorkbook;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.IOException;
    import java.util.Iterator;
    
    public class ApachePOIExcelRead {
    
        private static final String FILE_NAME = "/tmp/MyFirstExcel.xlsx";
    
        public static void main(String[] args) {
    
            try {
    
                FileInputStream excelFile = new FileInputStream(new File(FILE_NAME));
                Workbook workbook = new XSSFWorkbook(excelFile);
                Sheet datatypeSheet = workbook.getSheetAt(0);
                Iterator<Row> iterator = datatypeSheet.iterator();
    
                while (iterator.hasNext()) {
    
                    Row currentRow = iterator.next();
                    Iterator<Cell> cellIterator = currentRow.iterator();
    
                    while (cellIterator.hasNext()) {
    
                        Cell currentCell = cellIterator.next();
                        //getCellTypeEnum shown as deprecated for version 3.15
                        //getCellTypeEnum ill be renamed to getCellType starting from version 4.0
                        if (currentCell.getCellTypeEnum() == CellType.STRING) {
                            System.out.print(currentCell.getStringCellValue() + "--");
                        } else if (currentCell.getCellTypeEnum() == CellType.NUMERIC) {
                            System.out.print(currentCell.getNumericCellValue() + "--");
                        }
    
                    }
                    System.out.println();
    
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    }

    On executing the above code, you get the below output.

    Datatype--Type--Size(in bytes)--
    int--Primitive--2.0--
    float--Primitive--4.0--
    double--Primitive--8.0--
    char--Primitive--1.0--
    String--Non-Primitive--No fixed size--

    References

    1. Details about deprecation of getCellTypeEnum
    2. Apache POI reference regarding Deprecation
    3. Apache POI Maven Repo
    4. Apache POI API docs
  • 相关阅读:
    rpm的制作 spec文件写法
    RPM 打包技术与典型 SPEC 文件分析
    生成器
    闭包
    内置函数
    函数递归
    高阶函数
    匿名函数
    文件操作
    bytes
  • 原文地址:https://www.cnblogs.com/ys-wuhan/p/6359270.html
Copyright © 2011-2022 走看看