Writing a long (primitive type) to a file in Java

Question

Hi all,

I have an array of long that I would like to write into a .txt file that I can later open in gedit (one number per line). I get those values by using a subtraction of two instances of System.currentTimeMillis().

I use the following code:

BufferedWriter out = new BufferedWriter(new FileWriter("latency.txt"));
for (int i = 0; i < USER_LIMIT; ++i) {
    out.write(latency[i] + "\n");
}
out.close();

When looking at the file, I do see:

0
1
1
0

I believe the string concatenation converted the long into an integer. If I use the DataOutputStream, then I cannot read it back with gedit or any notepad/text editor, it just looks like garbage (I believe it's writing bytes).

Would anyone please let me know how I can fix my problem please?

Thank you very much!

Solution

There is nothing wrong with your code. What you think is in latency ... isn't.

public static void main(String[] args) throws IOException
{
    long[] latency = { 123456789000L, 234567890000L, 345678901000L };

    BufferedWriter out = new BufferedWriter(new FileWriter("latency.txt"));
    for (int i = 0; i < 3; ++i) {
        out.write(latency[i] + "\n");
    }
    out.close();
}

produces:

$ more latency.txt 
123456789000
234567890000
345678901000

When you're having a problem with code like this, it's often beneficial to write a small test case to narrow down the problem.