Cant get SQL results to write to file Java

Question

The title says it all. This is my ResultSet code:

try {
    while (rs.next()) {
        int ID  = rs.getInt("ID");
        String Name = rs.getString("Name");
        String CountryCode = rs.getString("CountryCode");
        String District = rs.getString("District");
        int Population = rs.getInt("Population");

        //Display values
        try {
            writeToFile(ID, Name, CountryCode, District, Population);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

This is my writeToFile method:

public void writeToFile(int id, String name, String countryCode, String district, int population) throws IOException {
    FileWriter fw = new FileWriter("C:\\Users\\horry\\Desktop\\results.txt");
    fw.write(id + " " + name + " " + countryCode + " " + district + " " + population + "\n");
    try {
        fw.flush();
        fw.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Ive tried the usual flush and close method but something is missing. Should the filewriter be declared elsewgere?

No exceptions. One line gets written but with an incorrect ID. Do you know a better method? — Neil A Jones, Jun 05 '17 at 19:20
Can you use the debugger (or logging) to see if the name, countryCode, etc. variables are being populated (or write a test case that passes in hard coded values for these parameters)? — John, Jun 05 '17 at 19:42

Ori Marko · Answer 1 · 2017-06-06T04:59:18.530

2

Try to open file with append option

 FileWriter fw = new FileWriter("C:\\Users\\horry\\Desktop\\results.txt", true);

To add new line in any platform (e.g. linux ) use general line seperator as below

fw.write(id + " " + name + " " + countryCode + " " + district + " " + population + System.getProperty("line.separator"));

edited Jun 06 '17 at 04:59

answered Jun 05 '17 at 19:19

Ori Marko

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This worked in the sense that my file is now filled. Any thoughts on creating new lines for each query? – Neil A Jones Jun 05 '17 at 19:22
updated with new line for each query, please accept the answer if it works – Ori Marko Jun 06 '17 at 04:59

Comencau · Answer 2 · 2017-06-05T21:09:19.053

You are opening a new FileWriter for each iteration of your ResultSet. By default a FileWriter writes at the beginning of the file. So you are continously overwritting what you have written in the file at the previous iteration.

Furthermore, I would advice to not create a new FileWriter at each iteration. I would open a FileWriter just one time and use the same one for all the ietrations.

Then, use a BufferedWriter instead of a pure FileWriter. It will be much faster.

Also, close the writer in a finally block, not within the try. Since Java 7, you can even use try-with-resources.

Finally, use br.newLine(); to write a new line instead of managing the "\n" yourself.

Please check the code below

File f = new File("C:\\Users\\horry\\Desktop\\results.txt");
try (BufferedWriter bw = new BufferedWriter(new FileWriter(f))) {
    while (rs.next()) {
        int id  = rs.getInt("ID");
        String name = rs.getString("Name");
        String countryCode = rs.getString("CountryCode");
        String district = rs.getString("District");
        int population = rs.getInt("Population");
        bw.write(id + " " + name + " " + countryCode + " " + district + " " + population);
        bw.newLine();
    }
}

Cant get SQL results to write to file Java

2 Answers2