How can I Cache the data I'm reading from a collection of text files in a directory using a TreeMap?

Question

How can I Cache the data I'm reading from a collection of text files in a directory using a TreeMap? Currently my program reads the data from several text files in a directory and the saves that information in a text file called output.txt. I would like to cache this data in order to use it later. How can I do this using the TreeMap Class? These are the keys,values: TreeMap The data I'd like to Cache is (date from the file, time of the file, current time).
import java.io.*;
public class CacheData {
  public static void main(String[] args) throws IOException {
  String target_dir = "C:\\Files";
  String output = "C:\\Files\output.txt";
  File dir = new File(target_dir);
  File[] files = dir.listFiles();
  // open the Printwriter before your loop
  PrintWriter outputStream = new PrintWriter(output);
  for (File textfiles : files) {
  if (textfiles.isFile() && textfiles.getName().endsWith(".txt")) {
  BufferedReader inputStream = null;
  // close the outputstream after the loop
  outputStream.close();
  try {
  inputStream = new BufferedReader(new FileReader(textfiles));
  String line;
  while ((line = inputStream.readLine()) != null) {
  System.out.println(line);
  // Write Content
  outputStream.println(line);
  } finally {
  if (inputStream != null) {
  inputStream.close();

Answer 1

How can I Cache the data I'm reading from a collection of text files in a directory using a TreeMap? Currently my program reads the data from several text files in a directory and the saves that information in a text file called output.txt. I would like to cache this data in order to use it later. How can I do this using the TreeMap Class?
I don't understand your question.
If you don't know how to use TreeMap why do you think a TreeMap is the correct solution for what you want to do?
If you are just asking how to use TreeMap then there are PLENTY of tutorials on the internet and the Java API provides the methods that area available.
TreeMap (Java Platform SE 7 )
Are you sure you want a map and not a tree instead?
https://docs.oracle.com/javase/tutorial/uiswing/components/tree.html