Java Matcher: How to match multiple lines with one regex

Question

My method takes a file, and tries to extract the text between the header ###Title### and closing ###---###. I need it to extract multiple lines and put each line into an array. But since readAllLines() converts all lines into an array, I don't know how to compare and match it.

public static ArrayList<String> getData(File f, String title) throws IOException {
    ArrayList<String> input = (ArrayList<String>) Files.readAllLines(f.toPath(), StandardCharsets.US_ASCII);
    ArrayList<String> output = new ArrayList<String>();

    //String? readLines = somehow make it possible to match
    System.out.println("Checking entry.");

    Pattern p = Pattern.compile("###" + title + "###(.*)###---###", Pattern.DOTALL);
    Matcher m = p.matcher(readLines);
    if (m.matches()) {
        m.matches();
        String matched = m.group(1);
        System.out.println("Contents: " + matched);
        String[] array = matched.split("\n");
        ArrayList<String> array2 = new ArrayList<String>();
        for (String j:array) {
            array2.add(j);
        }
        output = array2;
    } else {
        System.out.println("No matches.");
    }
    return output;
}

Here is my file, and I'm 100% sure that the compiler is reading the correct one.

###Test File###
Entry 1
Entry 2
Data 1
Data 2
Test 1
Test 2
###---###

The output says "No matches." instead of the entries.

Answer 1

You don't need regex for that. It's enough to loop through the array and compare items line by line, taking those between the start and end tags.

ArrayList<String> input = (ArrayList<String>) Files.readAllLines(f.toPath(), StandardCharsets.US_ASCII);
ArrayList<String> output = new ArrayList<String>();

boolean matched = false;
for (String line : input) {
    if (line.equals("###---###") && matched) matched = false; //needed parentheses
    if (matched) output.add(line);
    if (line.equals("###Test File###") && !matched) matched = true;
}

Answer 2

As per your comment, if they are going to be in the same way as posted, then i don't think regex is needed for this requirement. You can read line by line and do a contains of '###'

public static void main(String args[])
  {
  ArrayList<String> dataList = new ArrayList<String>();
  try{
  // Open the file that is the first 
  // command line parameter
  FileInputStream fstream = new FileInputStream("textfile.txt");
  // Get the object of DataInputStream
  DataInputStream in = new DataInputStream(fstream);
  BufferedReader br = new BufferedReader(new InputStreamReader(in));
  String strLine;
  //Read File Line By Line
  while ((strLine = br.readLine()) != null)   {
  // this line will skip the header and footer with '###'
  if(!strLine.contains("###");
   dataList.add(strLine);
  }
  //Close the input stream
  in.close();
    }catch (Exception e){//Catch exception if any
  System.err.println("Error: " + e.getMessage());
  }
  }
//Now dataList has all the data between ###Test File### and ###---###
}

You can also change the contains method parameter according to your requirement to ignore lines!