Concatenate multiple files

Question

I am trying to concatenate multiple text files. The program is working correctly, but if I do not know the total number of files, then how should the for loop be changed?

public class MultipleMerge {

    public static void main(String[] args) {
        BufferedReader br = null;
        BufferedWriter bw = null;

        String inFileName = "C:\\Users\\dokania\\Desktop\\Bio\\Casp10\\fasta\\out";
        File file = new File("C:\\Users\\dokania\\Desktop\\New folder\\out.txt");

        try {
            String s;

            int fileCounter = 0;
            FileWriter fw = new FileWriter(file.getAbsoluteFile());
            bw = new BufferedWriter(fw);

            for (fileCounter = 0; fileCounter < 157; fileCounter++) {
                br = new BufferedReader(new FileReader(inFileName + (fileCounter++) + ".fa"));

                while ((s = br.readLine()) != null) {
                    bw.write(s + "\n");
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (br != null) {
                    br.close();
                    bw.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

score 2 · Answer 1 · answered Jun 29 '15 at 17:59

2

Try get an array of Files in directory:

File[] array = new File("C:\\Users\\dokania\\Desktop\\Bio\\Casp10\\fasta\\").listFiles();

And then go through all files using foreach cycle

for(File file:array){
    //...
}

Maybe you'll need to use FileFilter:
http://docs.oracle.com/javase/7/docs/api/java/io/FileFilter.html
in method listFiles()

answered Jun 29 '15 at 17:59

maskacovnik

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I did not get it still. instead of using number 157. I am trying to do multiple file automatically – Unknown Jun 29 '15 at 18:16
`listFiles()` metod gives you array of files, so `array.length` is count of files (it maybe adds +2 because of `.` and `..` dirs - for this you can use `FileFilter`) @GauravDokania – maskacovnik Jun 29 '15 at 18:20
but there is a `BufferedReader`, I am confused @JackWhiteIII – maskacovnik Jun 29 '15 at 18:24
1

Very nice answer, +1 especially because I learned something new. – JackWhiteIII Jun 29 '15 at 18:26

score 1 · Answer 2 · answered Jun 29 '15 at 17:57

You could use command line arguments:

public class CommandLineTest {
    public static void main(String[] args) {
        int howManyFiles = Integer.parseInt(args[0]);
    }
}

Above code gives you the first command line argument and treats it as an integer. In your code, you should check if there really is an integer specified, though.

Concatenate multiple files

2 Answers2