How to style a row using POI

/*To style a row a cellStyle instance to be used in POI API and below steps are to be performed*/

/*Create an instance of HSSFCellStyle and it can be created as below
Below wb corresponds to HSSFWorkbook() class
wb = new HSSFWorkbook();
 */

HSSFCellStyle cellStyle = wb.createCellStyle();

/*Then a setFillForegroundColor method to be called using the color index. The color index is a short variable and defined as below*/

cellStyle.setFillForegroundColor(HSSFColor.GREY_25_PERCENT.index);

/*A setFillPattern method is to be called with another short variable to be sent as a variable*/

cellStyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);

/*Finally a cellStyle variable is ready and can be used to apply style but note that this style will be over written when you try to write value in the cell*/
/*The same style should be applied when writing the cellValue as shown further in the code*/

header.setRowStyle(cellStyle);

/*This creates a cell with value as 'Sample value' not this will remove the styling applied to the row and hence the styling should be applied again*/ 

header.createCell(1).setCellValue("Sample value");

/*As explained before the styling pattern is applied again*/

header.getCell(1).setCellStyle(cellStyle);
fileOutputStream = new FileOutputStream(filePath +"\\ExcelUtilities.xls");
wb.write(fileOutputStream);
fileOutputStream.close();