CODEWITHSUNDEEP
java
Jacob Books
Jacob Books

Reputation: 21

How to append java output to text file?

The program I have below works perfectly when I print it out in the Java console but when I try to append the program to be put into a text file, it only prints 1/5 of the student's averages into the appending text file.

 Bobby, average = 93

I want it to be printing all 5 student's averages as so

 Agnes, average = 76
 Bufford, average = 91
 Julie, average = 94
 Alice, average = 39
 Bobby, average = 93

Thanks in advance.

 import java.util.*;
 import java.io.*;
 public class StudentAverage {
 public static void main(String[]args) throws IOException {


 Scanner scanner = new Scanner(new        
 File("D:\\School\\StudentGrades.txt"));

 while (scanner.hasNextLine()) {

    Scanner scanners = new Scanner(scanner.nextLine());

    String name = scanners.next(); 
    double total = 0;
    int num = 0;

    while (scanners.hasNextInt()) { 
        total += scanners.nextInt();
        num++;
    }

    PrintStream output = new PrintStream (("D:\\School\\WriteStudentAverages.txt"));
    output.print(name + ", average = " + (Math.round(total/num)));
    output.flush();
}
scanner.close();
}
}

Upvotes: 0

Views: 762

Answers (3)

morido
morido

Reputation: 1017

There are a few more glitches in your code. Since you need to manage both the Scanner as well as the PrintWriter with a try/resource-construct, I'd prefer to keep the input- and output-routines separate and read the relevant contents of your file temporarily into memory.

Here is an idea:

LinkedHashMap<String, Integer> students = new LinkedHashMap<>();

// Input routine
try (Scanner scanner = new Scanner(new File("D:\\School\\StudentGrades.txt"))) {
    while (scanner.hasNextLine()) {
        try (Scanner scanners = new Scanner(scanner.nextLine())) {
            String name = scanners.next(); 
            int total = 0;
            int num = 0;

            while (scanners.hasNextInt()) { 
                total += scanners.nextInt();
                num++;
            }

            students.put(name, (int) Math.round((double)total/num));
        }       
    }
}
catch (FileNotFoundException e) {
    // do something smart
}

// Output routine
try (PrintStream output = new PrintStream ("D:\\School\\WriteStudentAverages.txt")) {
    for (Entry<String, Integer> student : students.entrySet()) {
        output.println(student.getKey() + ", average = " + Integer.toString(student.getValue()));       
    }
}
catch (FileNotFoundException e) {
    // do something smart
}

The above also allows you to get rid of that nasty throws IOException in the signature of your main()-method. Instead, there are now two beautiful skeletons of an exception handler (the two catch blocks) where you can put some logic that triggers in case

  • the input file has not been found / is not readable (first catch)
  • the output file isn't writable / cannot be created (second catch)

Upvotes: 0

ST-DDT
ST-DDT

Reputation: 2707

To append your output/text file you have to use a different way of writing it.

I also suggest using try-with-resource blocks to avoid memeory leaks.

try (OutputStream output = new FileOutputStream("myFile.txt", true);
        Writer writer = new OutputStreamWriter(output)) {
    writer.write(name + ", average = " + (Math.round(total / num)) + '\n');
}

You don't have to flush/close them manually

Upvotes: 1

Noam Mansur
Noam Mansur

Reputation: 362

PrintStream output = new PrintStream (("D:\\School\\WriteStudentAverages.txt"));

every time it gets to this line, it deletes the file ,opens a new file and adds only the current line. write this line before the loop, and in the loop just leave your other code as is.

Upvotes: 3

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