IText制作PDF表格，表格线粗细不一致

明显表格线粗细不一致，求原因代码：
Document document = new Document();
try {
PdfWriter.getInstance(document, new FileOutputStream("C:\\添加标题1.pdf"));
document.open();
PdfPTable table2 = new PdfPTable(2);
String[] data1={"1","1","1","1","1","1","1","1","1"};
//String[] data2={"S13282","赵存礼"," "," "," "," "," "," "};
for(int i=0;i<data1.length;i++){
PdfPCell cell=new PdfPCell(new Paragraph(data1[i])); 
 //cell.setFixedHeight(25);
 //cell.setHorizontalAlignment(Element.ALIGN_CENTER);
 //cell.setVerticalAlignment(Element.ALIGN_MIDDLE);
//cell.setBorderWidth(0.5f);
table2.addCell(cell);

} document.add(table2);
document.close();
} catch (Exception e) {

// TODO Auto-generated catch block
e.printStackTrace();
}