import java.io.BufferedReader;

import java.io.File;

import java.io.FileReader;

import java.io.IOException;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

public class TextFileIndexer {

public static Map<String, List<String>> indexTextFiles(String directoryPath) {

Map<String, List<String>> index = new HashMap<>();

File directory = new File(directoryPath);

if (!directory.exists() || !directory.isDirectory()) {

System.err.println("Invalid directory path: " + directoryPath); //Error handling

return index;

}

File[] files = directory.listFiles();

if (files != null) {

for (File file : files) {

if (file.isFile() && file.getName().toLowerCase().endsWith(".txt")) {

try (BufferedReader reader = new BufferedReader(new FileReader(file))) {

String line;

while ((line = reader.readLine()) != null) {

// Tokenize the line (simple example: split by spaces)

String[] tokens = line.toLowerCase().split("\\s+");

for (String token : tokens) {

if (!token.isEmpty()) { // Avoid empty tokens

index.computeIfAbsent(token, k -> new ArrayList<>()).add(file.getName());

}

}

}

} catch (IOException e) {

System.err.println("Error reading file: " + file.getName() + " - " + e.getMessage()); //Error handling

}

}

}

}

return index;

}

public static void main(String[] args) {

// Example usage:

String directoryPath = "test_files"; // Replace with your directory

Map<String, List<String>> index = indexTextFiles(directoryPath);

// Print the index (optional)

for (Map.Entry<String, List<String>> entry : index.entrySet()) {

System.out.println(entry.getKey() + ": " + entry.getValue());

}

}

}