inputフォームのカンマ設定処理

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

@GetMapping("/search")
public String searchProjects(
@RequestParam(required = false) String startDate,
@RequestParam(required = false) String endDate,
Model model
) {
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");

LocalDateTime start = (startDate != null && !startDate.isEmpty()) 
                      ? LocalDate.parse(startDate, formatter).atStartOfDay() 
                      : null;

LocalDateTime end = (endDate != null && !endDate.isEmpty()) 
                    ? LocalDate.parse(endDate, formatter).atTime(23, 59, 59) 
                    : null;

List<Project> projects = projectService.searchByContractDate(start, end);
model.addAttribute("projects", projects);
return "search";

}