java - 尽管我多次运行程序，如何才能只打印一次 pw.println 的三个语句

Question

即使我多次运行该程序，我也只尝试打印一次 pw.println 语句。有什么解决办法吗？

public static void main(String[] args) throws IOException {
    // TODO code application logic here
 Scanner a=new Scanner (System.in);
 String First_Name , Last_Name, Address , E_mail , Department;
 int Password;
 System.out.println("ENTER FIRST NAME: ");
 First_Name=a.next();
 System.out.println("ENTER LAST NAME: ");
 Last_Name=a.next();
 System.out.println("ENTER ADDRESS: ");
 Address=a.next();
 System.out.println("ENTER E_MAIL: ");
 E_mail=a.next();
 System.out.println("ENTER DEPARTMENT: ");
 Department=a.next();
 System.out.println("ENTER PASSWORD: ");
 Password=a.nextInt();      
 FileWriter fw=new FileWriter("C:\\Users\\HP\\Desktop\\STUD_INFO.txt" , true);
 PrintWriter pw=new PrintWriter (fw);
 pw.println("\t\t\t\t\t\tSTUDENT INFORMATION");
 pw.println("---------------------------------------------------------------------------------------------------------------------------------------------------");
 pw.println("First_Name" + "\t\t    " + "Last_Name" + "\t\t    " + "Address" + "\t\t    " + "E_mail" + "\t\t    " + "Department" + "\t\t    " + "Password");
 pw.println(First_Name   + "\t\t\t    " + Last_Name + "\t\t    " + Address + "\t\t    " + E_mail + "\t    " + Department + "\t\t\t    " + Password);  
 pw.close();
}

Answer 1

正如 Crusha 指出的那样，在将输出打印到文件中之前检查该文件是否存在。例如:

File f = new File("C:\\Users\\HP\\Desktop\\STUD_INFO.txt");
FileWriter fw=new FileWriter("C:\\Users\\HP\\Desktop\\STUD_INFO.txt" , true);
PrintWriter pw=new PrintWriter (fw);
if (!f.exists()) {
    pw.println("\t\t\t\t\t\tSTUDENT INFORMATION");
    pw.println("---------------------------------------------------------------------------------------------------------------------------------------------------");
    pw.println("First_Name" + "\t\t    " + "Last_Name" + "\t\t    " + "Address" + "\t\t    " + "E_mail" + "\t\t    " + "Department" + "\t\t    " + "Password");
}
pw.println(First_Name   + "\t\t\t    " + Last_Name + "\t\t    " + Address + "\t\t    " + E_mail + "\t    " + Department + "\t\t\t    " + Password);