Using group of regular expressions in java

Question

i'm writing a program which should change text file with regex. I have a few commands, and they are working in eg NotePad++. I want now the same commands in java to make it faster. Can it be caused by the way it saves and reads the file?

private List<String> lines = new ArrayList<String>(10000000);

// read original file to an ArrayList
public String[] readOriginalFile(String filename) throws IOException {
    FileReader fileReader = new FileReader(filename);
    BufferedReader bufferedReader = new BufferedReader(fileReader);
    String line = null;
    while (((line = bufferedReader.readLine()) != null)){
        lines.add(line);
    }
    bufferedReader.close();
    return lines.toArray(new String[lines.size()]);
}

 public void replaceWordsOne() {
    ArrayList<String> lns = new ArrayList<String>(10000000);
    for (String ln : lines) {
        lns.add(ln.replaceAll("^(\\[.*?\\])\\s+(\\[.*?\\])\\s(\\[.*?\\]\\s){1,}(\\[.*?\\])", "\1\t\2\t\4\t"));
    }
    lines.clear();
    lines = lns;
}

public void writeToNewFileOne(String FinalDirectory) throws IOException {
    FileWriter writer = new FileWriter(FinalDirectory);
    for (String str : lines) {
        writer.write(str +"\n");
    }
    writer.close();
}

Answer 1

i think that the main cause is this line:

private List<String> lines = new ArrayList<String>(10000000);

in java arraylist are dynamic resize arrays, that's means that you don't need to initialize the list with elements.

should be like this:

private List<String> lines = new ArrayList<String>();