자바 POI 는 엑셀 셀 내용 의 줄 바 꾸 기 를 어떻게 실현 합 니까?

	  <dependency>
   			<groupId>org.apache.poi</groupId>
   			<artifactId>poi</artifactId>
   			<version>3.15</version>
  		</dependency>
  		<dependency>
   			<groupId>org.apache.poi</groupId>
   			<artifactId>poi-ooxml</artifactId>
   			<version>3.15</version>
  		</dependency>
  		
  		
  		<dependency>
   			<groupId>commons-io</groupId>
   			<artifactId>commons-io</artifactId>
   			<version>2.5</version>
  		</dependency>

@RestController
public class MyController {
	@RequestMapping("/ip/v5")
	public void getExcel(HttpServletResponse response) throws IOException {
		ArrayList<String> arrayList = new ArrayList<String>();
		arrayList.add("this is     1 ");
		arrayList.add("this is     2 ");
		arrayList.add("this is     3 ");
		arrayList.add("this is     4 ");
		
		XSSFWorkbook workBook = new XSSFWorkbook();
		XSSFSheet sheet = workBook.createSheet();
		workBook.setSheetName(0, "ip-v4 ");
		XSSFCellStyle cs = workBook.createCellStyle(); //      ，            
		cs.setWrapText(true);
		String fileName = "china-ip-v4" + ".xls";//            
		String[] headers = { "  " };
		XSSFRow titleRow = sheet.createRow(0);
		//  excel      
		for (int i = 0; i < headers.length; i++) {
			titleRow.createCell(i).setCellValue(headers[i]);
		}
		String content = String.join("
", arrayList);
		int rowNum = 1;
		XSSFRow row1 = sheet.createRow(rowNum); //     
		XSSFCell cell = row1.createCell(0); //        
		//        
		//cell.setCellValue("this is     1  
 this is    2  
 this is     3  
 this is     4 ");
		cell.setCellValue(content);
		cell.setCellStyle(cs);
		response.setContentType("application/octet-stream");
		response.setHeader("Content-disposition", "attachment;filename=" + fileName);
		response.flushBuffer();
		workBook.write(response.getOutputStream());
	}
}

String str="  \r
  "