如何使用PDFBox居中文本

PDDocument document = new PDDocument();

PDPage page = new PDPage();
document.addPage(page);

PDFont font = PDType1Font.HELVETICA_BOLD;

float fontSize = 12;
float leading = 1.5f; // 行间距
float margin = 50; // 页面边距
float width = page.getMediaBox().getWidth() - 2 * margin;
float startX = margin;
float startY = page.getMediaBox().getHeight() - margin;

String text = "居中文本";
float textWidth = font.getStringWidth(text) / 1000 * fontSize;
float startX = (page.getMediaBox().getWidth() - textWidth) / 2;

PDPageContentStream contentStream = new PDPageContentStream(document, page);
contentStream.setFont(font, fontSize);
contentStream.beginText();
contentStream.newLineAtOffset(startX, startY);
contentStream.showText(text);
contentStream.endText();
contentStream.close();

document.save("path/to/output.pdf");
document.close();