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POReading file and adding text to random character location
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copied!<p>I have a text file with a sequence of 4194304 letters ranging from A-D all on one line (4 MB). How would I randomly point to a character and replace the following set of characters to another file that is 100 characters long and write it out to a file? I'm actually currently able to do this, but I feel it's really inefficient when I iterate it several times.</p> <p>Here's an illustration of what I mentioned above: <a href="http://desmond.imageshack.us/Himg716/scaled.php?server=716&filename=goalw.jpg&res=landing" rel="nofollow">Link to Imageshack</a></p> <p>Here's how I'm currently achieving this:</p> <pre><code>Random rnum = new Random(); FileInputStream fin = null; FileOutputStream fout = null; int count = 10000; FileInputStream fin1 = null; File file1 = new File("fileWithSet100C.txt"); int randChar = 0; while(cnt > 0){ try { int c = 4194304 - 100; randChar = rnum.nextInt(c); File file = new File("file.txt"); //seems inefficient to initiate these guys over and over fin = new FileInputStream(file); fin1 = new FileInputStream(file1); //would like to remove this and have it just replace the original fout = new FileOutputStream("newfile.txt"); int byte_read; int byte_read2; byte[] buffer = new byte[randChar]; byte[] buffer2 = new byte[(int)file1.length()]; //4m byte_read = fin.read(buffer); byte_read2 = fin1.read(buffer2); fout.write(buffer, 0, byte_read); fout.write(buffer2, 0, byte_read2); byte_read = fin.read(buffer2); buffer = new byte[4096]; //4m while((byte_read = (fin.read(buffer))) != -1){ fout.write(buffer, 0, byte_read); } cnt--; } catch (...) { ... } finally { ... } try{ File file = new File("newfile.txt"); fin = new FileInputStream(file); fout = new FileOutputStream("file.txt"); int byte_read; byte[] buffer = new byte[4096]; //4m byte_read = fin.read(buffer); while((byte_read = (fin.read(buffer))) != -1){ fout.write(buffer, 0, byte_read); } } catch (...) { ... } finally { ... } </code></pre> <p>Thanks for reading!</p> <p>EDIT: For those curious, here's the code I used to solve the aforementioned problem:</p> <pre><code>String stringToInsert = "insertSTringHERE"; byte[] answerByteArray = stringToInsert.getBytes(); ByteBuffer byteBuffer = ByteBuffer.wrap(answerByteArray); Random rnum = new Random(); randChar = rnum.nextInt(4194002); //4MB worth of bytes File fi = new File("file.txt"); RandomAccessFile raf = null; try { raf = new RandomAccessFile(fi, "rw"); } catch (FileNotFoundException e1) { // TODO error handling and logging } FileChannel fo = null; fo = raf.getChannel(); // Move to the beginning of the file and write out the contents // of the byteBuffer. try { outputFileChannel.position(randChar); while(byteBuffer.hasRemaining()) { fo.write(byteBuffer); } } catch (IOException e) { // TODO error handling and logging } try { outputFileChannel.close(); } catch (IOException e) { // TODO error handling and logging } try { randomAccessFile.close(); } catch (IOException e) { // TODO error handling and logging } </code></pre>

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