Java PrintWriter只显示一条来自mysql数据库的记录

Question

我使用writer.println在新行上显示每条记录。当我使用system.out.println时，所有所需的记录都从数据库中取出，并正确地显示在控制台上。但是，当我试图写入文件时，只显示一条记录。请帮帮忙。

我的密码：

Scanner input = new Scanner(System.in);
    System.out.print("Kindly enter the lowest CPA threshold : ");
    cpa1 = input.nextFloat();

    System.out.println();

    System.out.println("Kindly enter highest CPA threshold : ");
    cpa2 = input.nextFloat();

    String query = "SELECT * FROM student WHERE CPA BETWEEN ? and ? order by CPA asc";
    stt = conn.prepareStatement(query);
    stt.setFloat(1, cpa1);
    stt.setFloat(2, cpa2);
    rs = stt.executeQuery();

    PrintWriter writer = new PrintWriter("StudentRange.txt");
    writer.println("Student ID \t Student Name \t Gender\t CPA\t Enrolment Date");
    System.out.println("Student ID \t Student Name \t Gender\t CPA\t Enrolment Date");
     while(rs.next()){
         String id = rs.getString("student_id");
         String name = rs.getString("student_name");
         String gender = rs.getString("gender");
         float cpa = rs.getFloat("CPA");
         Date enrol = rs.getDate("enrollment_date");

         try{


            writer.println();
            writer.println(id + "\t\t" + name + "\t" + gender + "\t" + cpa + "\t" + enrol);
            System.out.println(id + "\t\t" + name + "\t" + gender + "\t" + cpa + "\t" + enrol);
            writer.close();


         }catch(Exception e){
             e.printStackTrace();
         }

Answer 1

不要在第一行之后关闭作者：)

writer.close();

应该是在while循环结束之后。

类似于：

while(rs.next()){
  //... code goes here
}
writer.close();