Using BufferedWriter to write to a string

Question

I am trying to use a BufferedWriter to switch between writing to a File and writing to a String, but I have never used a BufferedWriter to write to anything but a file.

Take this compilable code:

public static void main(String[] args) {
    try (BufferedWriter fileWriter = new BufferedWriter(new FileWriter(new File("file.txt")));
            StringWriter sw = new StringWriter();
            BufferedWriter stringWriter = new BufferedWriter(sw)) {

        LinkedList<Record> records = new LinkedList<>();
        records.add(new Record("name1", "text1", 20.4));
        records.add(new Record("name2", "text2", -78));
        records.add(new Record("name3", "text3", 11.56));
        records.add(new Record("name4", "text4", 56));
        records.add(new Record("name3", "text3", -44));

        for(Record record : records) {
            BufferedWriter writer;
            if(record.amount < 0) {
                writer = stringWriter; // write to string if amount is less than zero
            } else {
                writer = fileWriter; // write to file if not
            }

            writer.append(record.name);
            writer.append(",");
            writer.append(record.text);
            writer.append(",");
            writer.append(String.valueOf(record.amount));
            writer.newLine();

        }

        String less_than_zero_amounts = sw.toString();
        System.out.println("Less than zero:" + less_than_zero_amounts);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

static class Record {
    String name;
    String text;
    double amount;

    public Record(String name, String text, double amount) {
        this.name = name;
        this.text = text;
        this.amount = amount;
    }

    public String getText() {
        return text;
    }

    public String getName() {
        return name;
    }

    public double getAmount() {
        return amount;
    }
}

The output for the file is (correctly)

name1,text1,20.4
name3,text3,11.56
name4,text4,56.0

But the output for the program does not print the StringWriter.

Admittedly, using a StringWriter and giving that to the BufferedWriter was a hunch. Any way I can switch a BufferedWriter to output to a String would solve the problem.

Answer 1

You need to call "flush()" to flush the contents of the buffer to the output: http://docs.oracle.com/javase/7/docs/api/java/io/BufferedWriter.html#flush()

Though I should add that rather than select between BufferedWriter objects, you probably want to simply select between Writer objects... the StringWriter has a buffer of its own, so there is no need to add an extra layer of a BufferedWriter on top of it.