@Test
public void testHSSF() throws Exception {
    //  创建一个工作簿
    HSSFWorkbook wb = new HSSFWorkbook();
    //  创建一个工作表
    HSSFSheet sheet = wb.createSheet();

    //  创建字体
    HSSFFont font1 = wb.createFont();
    HSSFFont font2 = wb.createFont();
    font1.setFontHeightInPoints((short) 14);
    font1.setColor(HSSFColor.HSSFColorPredefined.RED.getIndex());
    font2.setFontHeightInPoints((short) 12);
    font2.setColor(HSSFColor.HSSFColorPredefined.BLUE.getIndex());
    //  创建单元格样式
    HSSFCellStyle css1 = wb.createCellStyle();
    HSSFCellStyle css2 = wb.createCellStyle();
    HSSFDataFormat df = wb.createDataFormat();
    //  设置单元格字体及格式
    css1.setFont(font1);
    css1.setDataFormat(df.getFormat("#,##0.0"));
    css2.setFont(font2);
    css2.setDataFormat(HSSFDataFormat.getBuiltinFormat("text"));

    //  创建行
    for (int i = 0; i < 20; i++) {
        HSSFRow row = sheet.createRow(i);
        for (int j = 0; j < 10; j = j + 2) {
            HSSFCell cell = row.createCell(j);
            cell.setCellValue("Spring");
            cell.setCellStyle(css1);

            HSSFCell cell2 = row.createCell(j+1);
            cell2.setCellValue(new HSSFRichTextString("Hello! " + j));
            cell2.setCellStyle(css2);
        }
    }

    //  写文件
    FileOutputStream fos = new FileOutputStream("G:/wb.xls");
    wb.write(fos);
    fos.close();
}

@Test
public void testSS() throws IOException {
    Workbook[] wbs = {new HSSFWorkbook(), new XSSFWorkbook()};
    for (int i = 0; i < wbs.length; i++) {
        Workbook wb = wbs[i];
        CreationHelper creationHelper = wb.getCreationHelper();
        Sheet sheet = wb.createSheet();
        for (int j = 0; j < 10; j++) {
            Row row = sheet.createRow(j);
            Cell cell = row.createCell(0);
            cell.setCellValue(creationHelper.createRichTextString("ABC"));
        }

        String filename = "G:/workbook.xls";
        if (wb instanceof XSSFWorkbook) {
            filename = filename + "x";
        }
        wb.write(new FileOutputStream(filename));
        wb.close();
    }
}

@Test
public void abc() throws IOException {
    long t1 = System.currentTimeMillis();

    List<User> userList = new ArrayList<>();
    for (int i = 0; i < 100000; i++) {
        userList.add(new User("zhangsan", "10001"));
    }

    InputStream is = new FileInputStream("G:/object_collection_template.xlsx");
    OutputStream os = new FileOutputStream("G:/object_collection_out.xlsx");
    Context context = new Context();
    context.putVar("users", userList);
    JxlsHelper.getInstance().processTemplate(is, os, context);

    long t2 = System.currentTimeMillis();
    System.out.println(t2 - t1);
}

/**
 * 写一个工作表，窗口大小是100
 * 当达到101行的时候，行号为0的行（rownum=0）被刷新到磁盘，并从内存中删除
 * 当行号达到102的时候，rownum=1的行被刷新到磁盘，并从内存中删除
 * 也就是说内存中最多保存100行，就是一个滑动窗口
 */
@Test
public void testWindow() throws IOException {
    //  在内存中保存100行，当行数超过100时将其刷新到磁盘
    System.out.println(Runtime.getRuntime().freeMemory());

    SXSSFWorkbook wb = new SXSSFWorkbook(100);
    SXSSFSheet sheet = wb.createSheet();
    for (int i = 0; i < 1000; i++) {
        SXSSFRow row = sheet.createRow(i);
        for (int j = 0; j < 10; j++) {
            SXSSFCell cell = row.createCell(j);
            cell.setCellValue(new CellReference(cell).formatAsString());
        }
    }

    //  行号小于900的行已经被刷新到磁盘，无法访问
    for (int rownum = 0; rownum < 900; rownum++) {
        Assert.assertNull(sheet.getRow(rownum));
    }

    //  最后100行仍然在内存中
    for (int rownum = 900; rownum < 1000; rownum++) {
        Assert.assertNotNull(sheet.getRow(rownum));
    }

    FileOutputStream fos = new FileOutputStream("G:/sxssf.xlsx");
    wb.write(fos);
    fos.close();

    //  处理工作表在磁盘上产生的临时文件
    wb.dispose();
}

/**
 * 关闭自动刷新，并且手动控制哪些数据被写到磁盘
 */
@Test
public void testAutoFlush() throws IOException {
    //  关闭自动刷新，并且在内存中累积所有的行
    SXSSFWorkbook wb = new SXSSFWorkbook(-1);
    SXSSFSheet sheet = wb.createSheet();
    for (int rownum = 0; rownum < 1000; rownum++) {
        Row row = sheet.createRow(rownum);
        for (int cellnum = 0; cellnum < 10; cellnum++) {
            Cell cell = row.createCell(cellnum);
            cell.setCellValue(new CellReference(cell).formatAsString());
        }

        //  手动控制刷新多少行到磁盘
        if (rownum % 100 == 0) {
            //  保留最后100行，其余的刷新到磁盘
            sheet.flushRows(100);
//                sheet.flushRows();  //  所有行，全部刷新到磁盘
        }
    }

    FileOutputStream fos = new FileOutputStream("G:/sxssf2.xlsx");
    wb.write(fos);
    fos.close();

    //  删除产生的临时文件
    wb.dispose();
}

/**
 * SXSSF刷新工作表数据到磁盘（每个工作表一个临时文件），而且，临时文件可能会增长到非常大。
 * 例如，对于一个20M的csv数据它的临时xml数据有可能会变得超过1G
 * 如果你任务临时文件的的大小是一个问题的话，那么你可以告诉SXSSF用gzip来压缩它。
 * SXSSFWorkbook wb = new SXSSFWorkbook();
 * wb.setCompressTempFiles(true); // temp files will be gzipped
 */

<dependencies>
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-csv</artifactId>
        <version>1.5</version>
    </dependency>

    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi</artifactId>
        <version>3.17</version>
    </dependency>

    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-ooxml</artifactId>
        <version>3.17</version>
    </dependency>

    <dependency>
        <groupId>org.jxls</groupId>
        <artifactId>jxls</artifactId>
        <version>2.4.5</version>
    </dependency>

    <dependency>
        <groupId>org.jxls</groupId>
        <artifactId>jxls-poi</artifactId>
        <version>1.0.15</version>
    </dependency>


    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
</dependencies>