PrintWriter not writing to file (Java)

Question

I am writing a kind of a cash machine program that will output the data into a file (Yes, I know its not in English, but that\'s not the point) and I am experiencing an error.

Answer 1

public static void studentAdd() throws IOException ,ClassNotFoundException{

    DataOutputStream output = new DataOutputStream(new FileOutputStream("Student.txt"));
    PrintWriter pr = new PrintWriter("Student.txt");
    Student7 student[] = new Student7[total];
    int STOP = 999;
    int stdID;
    int age;
    String address;
    String gender;
    String name;

    Scanner input = new Scanner(System.in);
    System.out.println("Please type  student ID or 999 to quit");
    stdID = input.nextInt(); 

    try {
        while(stdID != STOP) {  
            input.nextLine();
            output.writeInt(stdID);
            pr.print(stdID + "#");

            System.out.println("Please type student name");
            name = input.nextLine();
            output.writeUTF(name);
            pr.print(name + "#");

            System.out.println("Please type student age");
            age = input.nextInt();
            output.writeInt(age);
            input.nextLine();
            pr.print(age + "#");

            System.out.println("Please type student gender");
            gender = input.nextLine();
            output.writeUTF(gender);
            pr.print(gender + "#");                     

            System.out.println("Please type student address");
            address = input.nextLine();
            output.writeUTF(address);
            pr.print(address + "#");
            pr.println();

            System.out.println("Please type  student ID or 999 to quit");
            stdID = input.nextInt();
            }
        ;   pr.close();
            output.close();

    } catch (IOException e) { 
        System.err.println("Error is" + e.getMessage());
    } catch(InputMismatchException e) {
        System.err.println("Invalid Data Entry");
    }finally {
        studentMenu();
    }

} //end of stuadd

Answer 2

Why are you opening and closing stream in your writeToFile call ? Shouldn't you open the streams in writeFooter() before the for loop, put a try block around the writing code, and close them in a finally section .

The way I see it, You've openedstream first in the writeFooter, the you write printer.println("Проданные товары: ");, and then your for loop's first iteration calls writeToFile, will again open the non-closed stream, that will surely overwrite the first printed line.

Opening and closing File for writing one line is way too inefficient.

You need something like

writeFooter(...) {

  try {
    openStreams();
    writeToFile();
  } finally {
    closeStream();
  }
}

Where writeToFile simply writes , doesn't open or close stream, and closeStream safely closes the streams, i.e. check for null etc.