Java BufferedFileWriter只写入50％的输入行

Question

My TAB-delimited input file has 1 million lines , it looks like this:

id  name    artist_name genre   notoriete_fr    notoriete_us    notoriete_uk    notoriete_it    notoriete_sp    notoriete_no    notoriete_de    notoriete_wd
1   10ème bougie   113 rap 0   -5  -5  -5  -5  -5  -5  -5
2   I'm not in love 10cc    pop 1   1   1   1   1   1   1   1
5   Generation  Black Rebel Motorcycle Club rock    0   0   0   0   0   0   0   0

I've coded a file format transformation, and the output file to looks like this:

id:ID;genre;notoriete_fr:int;notoriete_us:int;notoriete_uk:int;notoriete_sp:int;notoriete_de:int;notoriete_it:int;notoriete_no:int;notoriete_wd:int;:LABEL
t1;rap;0;-5;-5;-5;-5;-5;-5;-5;Track
t5;rock;0;0;0;0;0;0;0;0;Track

I have two problems :

• the output file only has 50% of input file lines
• the output file has missing lines, eg t2 's line is missing

Here's my code, thanks in advance!

Note: I've also added a buffer size to new BufferedWriter()/Reader() , no impact.

    public static void main(String[] args) throws Exception {

    BufferedReader br = null;
    BufferedWriter bw = null;

    try{

        // prepare input file
        File inFile = new File(inputFile);
        br = new BufferedReader(new FileReader(inFile));
        String line = "";
        String cvsSplitBy = "\t";           

        // prepare output file
        File outFile = new File(outputFile);            
        bw = new BufferedWriter(new FileWriter(outFile));

        // Write header
        bw.write("id:ID;genre;notoriete_fr:int;notoriete_us:int;notoriete_uk:int;notoriete_sp:int;notoriete_de:int;notoriete_it:int;notoriete_no:int;notoriete_wd:int;:LABEL\n");

        while ((line = br.readLine()) != null) {
            // READING
            line = br.readLine();
            String[] features = line.split(cvsSplitBy);
            // WRITING              
            bw.write("t"+features[0]+";"+features[3]+";"+features[4]+";"+features[5]+";"+features[6]+";"+features[7]+";"+features[8]+";"+features[9]+";"+features[10]+";"+features[11]+";Track\n");
        }

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (br != null) {
            try {
                br.close();
                bw.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
}

Answer 1

the output file only has 8.3% of input file lines

As far as you code is concerned, It should be 50% of the lines should be missing. You have the difference in size because the data that is in the parent file is of different format than that in the file you are creating. I am saying this because you code skips the alternate lines.

Let me explain, in your while loop condition you are using line = br.readLine() Which reads the line 1. now in the first line of the while loop you are again using line = br.readLine() this will read the line 2. the file. You are using it to write the data, so line 2 data gets written. Now in the second looping, in the while loop condition you are reading line 3 of the file and in the first line of while loop you are reading line 4 of the file and this line gets written. So you see you get 50% of the output.

Now you think you understand why you are getting lesser lines in the output file. so the simple solution is to get rid of preferable the first line of the while loop and let the condition remain the same.

Answer 2

this behavior can be attributed to the following two lines in the code.

while ((line = br.readLine()) != null) {
                // READING
                line = br.readLine();

you are reading two lines from the file one during while check and one during the line = br.readline() , causing skipped lines. you should read only at the while loop check.

   while ((line = br.readLine()) != null) {
     // use line variable value for printing