java 使用poi

package com.bigzhao.PoiTest;

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import java.io.FileOutputStream;

public class ExcelPoiTest {
    public static void main(String[] args) throws Exception {
        poiTest2();
    }

    public static void poiTest2()throws Exception{
        Workbook workbook = new XSSFWorkbook("C:\\Users\\LENOVO\\Desktop\\poiTest2.xlsx");
        // 获取sheet
        Sheet sheet = workbook.getSheetAt(0);
        // 获取sheet 中的每一行，和每一个单元格
        for (int rowNum =0; rowNum <= sheet.getLastRowNum();rowNum++ ){
            Row row = sheet.getRow(rowNum);
            StringBuilder builder = new StringBuilder();
            // 获取每一个单元格 cellNum 为什么是2 ？
            for (int cellNum =0; cellNum < row.getLastCellNum();cellNum++){
                // 获取索引里的每一个单元格
                Cell cell = row.getCell(cellNum);
                // 获取每一个单元格的内容
                Object value = getCellValue(cell);
                builder.append(value+"  ");
            }
            System.out.println(builder);
        }
    }
    public static Object getCellValue(Cell cell) {
        //1.获取到单元格的属性类型
        CellType cellType = cell.getCellType();
        //2.根据单元格数据类型获取数据
        Object value = null;
        switch (cellType) {
            case STRING:
                value = cell.getStringCellValue();
                break;
            case BOOLEAN:
                value = cell.getBooleanCellValue();
                break;
            case NUMERIC:
                if(DateUtil.isCellDateFormatted(cell)) {
                    //日期格式
                    value = cell.getDateCellValue();
                }else{
                    //数字
                    value = cell.getNumericCellValue();
                }
                break;
            case FORMULA: //公式
                value = cell.getCellFormula();
                break;
            default:
                break;
        }
        return value;
    }
    public static void poiTest1() throws Exception{
        // 创建工作表
        Workbook work = new XSSFWorkbook(); // 2007 版本
        // 创建表单 sheet
        Sheet sheet = work.createSheet();
        // 创建行
        Row row = sheet.createRow(2);
        // 创建列
        Cell cell = row.createCell(2);
        // 在单元格写入
        cell.setCellValue("Hello！");
        // 创建样式对象
        CellStyle style = work.createCellStyle();
        /*style.setBorderTop(BorderStyle.DASH_DOT);
        style.setBorderLeft(BorderStyle.DASH_DOT);
        style.setBorderRight(BorderStyle.DASH_DOT);
        style.setBorderBottom(BorderStyle.DASH_DOT);*/
        // 行高和列宽
        row.setHeightInPoints(50);
        sheet.setColumnWidth(3,31 * 256);//设置第几列，多宽（字符宽度）所以要除以256
        // 居中显示
        style.setAlignment(HorizontalAlignment.CENTER);
        style.setVerticalAlignment(VerticalAlignment.CENTER);
        // 创建字体对象
        Font font = work.createFont();
        font.setFontName("华文行楷");
        font.setFontHeightInPoints((short)28);
        style.setFont(font);
        // 将之前的样式全都添加到单元格中
        cell.setCellStyle(style);

        // 创建文件流
        FileOutputStream fo = new FileOutputStream("C:\\Users\\LENOVO\\Desktop\\poiTest1.xlsx");
        // 写入文件
        work.write(fo);
        fo.close();
    }


}