The maximum number of cell styles was exceeded. You can define up to 4000 styles

POI操作Excel中，导出的数据不是很大时，则不会有问题，而数据很多或者比较多时 ，

就会报以下的错误，是由于cell styles太多create造成，故一般可以把cellstyle设置放到循环外面

报错如下：

Caused by: java.lang.IllegalStateException: The maximum number of cell styles was exceeded. You can define up to 4000 styles in a .xls workbook
at org.apache.poi.hssf.usermodel.HSSFWorkbook.createCellStyle(HSSFWorkbook.java:1144)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.createCellStyle(HSSFWorkbook.java:88)
at com.trendmicro.util.toExcel.ExcelExporter.addWorkbook(ExcelExporter.java:612)
at com.trendmicro.util.toExcel.ExcelExporter.exportToExcel(ExcelExporter.java:112)
at com.trendmicro.util.toExcel.ReportExporter.exportAutomationReport(ReportExporter.java:190)
at com.trendmicro.view.reports.TestCaseAutomationBean.exportAutoReport(TestCaseAutomationBean.java:856)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.el.parser.AstValue.invoke(AstValue.java:191)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
at org.apache.jasper.el.JspMethodExpression.invoke(JspMethodExpression.java:68)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)

... 33 more

错误代码

private CellStyle ltdStyle(Workbook wb){
	CellStyle curStyle = wb.createCellStyle();
	Font curFont = wb.createFont();					//设置字体
	curFont.setFontName("宋体");
	curFont.setCharSet(Font.DEFAULT_CHARSET);		//设置中文字体，那必须还要再对单元格进行编码设置
		
	curFont.setBoldweight(Font.BOLDWEIGHT_BOLD);	//加粗
//	curFont.setItalic(true);
	curFont.setFontHeightInPoints((short)14);
	curStyle.setFont(curFont);
	curStyle.setVerticalAlignment(CellStyle.VERTICAL_CENTER);		//单元格垂直居中
		
	return curStyle;
} 	

for(int i=0;i<10000;i++){
    nRow.setHeightInPoints(60);
    region = new CellRangeAddress(curRow-1, curRow-1, 8, 13);
    sheet.addMergedRegion(region);
    nCell = nRow.createCell(8);
    nCell.setCellValue("考生须知");
    nCell.setCellStyle(this.ltdStyle(wb));//数据量较大时,调用createStyle次数太多造成上述错误
}

正确代码如下：

CellStyle title = this.ltdStyle(wb);//将设置单元格样式放在循环外面执行，就不会报上述错误
for(int i=0;i<10000;i++){
    nRow.setHeightInPoints(60);
    region = new CellRangeAddress(curRow-1, curRow-1, 8, 13);
    sheet.addMergedRegion(region);
    nCell = nRow.createCell(8);
    nCell.setCellValue("考生须知");
    nCell.setCellStyle(title);
}