package examples;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.nio.channels.FileChannel;

import java.nio.file.*;

import java.nio.charset.StandardCharsets;

import java.util.*;

import java.util.stream.Collectors;

public class NIOExample2 {

// Main method to test the implemented functionalities

public static void main(String[] args) {

try {

String inputFile = "C:\\Users\\aniru\\OneDrive\\Desktop\\Has-A_Time.txt";

String outputFile = "output.txt";

NIOFileProcessing.reverseFileContent(inputFile, "reversed.txt");

NIOFileProcessing.findAndReplace(inputFile, "replaced.txt", "Java", "NIO");

NIOFileProcessing.parseCSV("C:\\Users\\aniru\\OneDrive\\Desktop\\data.csv", "parsed.txt");

NIOFileProcessing.countWordFrequency(inputFile, "word_frequency.txt");

NIOFileProcessing.extractPalindromes(inputFile, "palindromes.txt");

} catch (IOException e) {

e.printStackTrace();

}

}

}

class NIOFileProcessing {

/**

* 1) Reverse Content of a Large File (NIO-based version)

* Reads a file using FileChannel, reverses each line, and writes it to another file.

*/

public static void reverseFileContent(String inputFile, String outputFile) throws IOException {

try (FileChannel inChannel = FileChannel.open(Paths.get(inputFile), StandardOpenOption.READ);

FileChannel outChannel = FileChannel.open(Paths.get(outputFile), StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {

ByteBuffer buffer = ByteBuffer.allocate(8192);

StringBuilder sb = new StringBuilder();

while (inChannel.read(buffer) > 0) {

buffer.flip();

sb.append(StandardCharsets.UTF_8.decode(buffer));

buffer.clear();

}

List<String> lines = Arrays.asList(sb.toString().split("\n"));

Collections.reverse(lines);

ByteBuffer outputBuffer = StandardCharsets.UTF_8.encode(String.join("\n", lines));

outChannel.write(outputBuffer);

}

System.out.println("File reversed successfully!");

}

/**

* 2) Find and Replace Words in a File (NIO-based version)

* Reads a file, replaces occurrences of a word, and writes to a new file using FileChannel.

*/

public static void findAndReplace(String inputFile, String outputFile, String target, String replacement) throws IOException {

try (FileChannel inChannel = FileChannel.open(Paths.get(inputFile), StandardOpenOption.READ);

FileChannel outChannel = FileChannel.open(Paths.get(outputFile), StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {

ByteBuffer buffer = ByteBuffer.allocate((int) inChannel.size());

inChannel.read(buffer);

buffer.flip();

String content = StandardCharsets.UTF_8.decode(buffer).toString();

content = content.replaceAll(target, replacement);

ByteBuffer outputBuffer = StandardCharsets.UTF_8.encode(content);

outChannel.write(outputBuffer);

}

System.out.println("Find and replace completed!");

}

/**

* 3) Custom CSV Parser (NIO-based version)

* Reads a CSV file using FileChannel, processes each line, and writes formatted output.

*/

public static void parseCSV(String inputFile, String outputFile) throws IOException {

try (FileChannel inChannel = FileChannel.open(Paths.get(inputFile), StandardOpenOption.READ);

FileChannel outChannel = FileChannel.open(Paths.get(outputFile), StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {

ByteBuffer buffer = ByteBuffer.allocate((int) inChannel.size());

inChannel.read(buffer);

buffer.flip();

String content = StandardCharsets.UTF_8.decode(buffer).toString();

List<String> parsedLines = Arrays.stream(content.split("\n"))

.map(line -> Arrays.toString(line.split(",(?=([^\"]*\"[^\"]*\")*[^\"]*$)"))) // Handling quoted CSV values

.collect(Collectors.toList());

ByteBuffer outputBuffer = StandardCharsets.UTF_8.encode(String.join("\n", parsedLines));

outChannel.write(outputBuffer);

}

System.out.println("CSV Parsing completed!");

}

/**

* 4) Word Frequency Counter in Large File (NIO-based version)

* Reads a file using FileChannel, counts word frequency, and writes results.

*/

public static void countWordFrequency(String inputFile, String outputFile) throws IOException {

try (FileChannel inChannel = FileChannel.open(Paths.get(inputFile), StandardOpenOption.READ);

FileChannel outChannel = FileChannel.open(Paths.get(outputFile), StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {

ByteBuffer buffer = ByteBuffer.allocate((int) inChannel.size());

inChannel.read(buffer);

buffer.flip();

String content = StandardCharsets.UTF_8.decode(buffer).toString().toLowerCase();

String[] words = content.split("\\W+");

Map<String, Integer> frequencyMap = new HashMap<>();

for (String word : words) {

frequencyMap.put(word, frequencyMap.getOrDefault(word, 0) + 1);

}

List<String> result = frequencyMap.entrySet().stream()

.map(entry -> entry.getKey() + " : " + entry.getValue())

.collect(Collectors.toList());

ByteBuffer outputBuffer = StandardCharsets.UTF_8.encode(String.join("\n", result));

outChannel.write(outputBuffer);

}

System.out.println("Word frequency count completed!");

}

/**

* 5) Extract Palindromes from a File (NIO-based version)

* Reads a file using FileChannel, extracts palindrome words, and writes them.

*/

public static void extractPalindromes(String inputFile, String outputFile) throws IOException {

try (FileChannel inChannel = FileChannel.open(Paths.get(inputFile), StandardOpenOption.READ);

FileChannel outChannel = FileChannel.open(Paths.get(outputFile), StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {

ByteBuffer buffer = ByteBuffer.allocate((int) inChannel.size());

inChannel.read(buffer);

buffer.flip();

String content = StandardCharsets.UTF_8.decode(buffer).toString();

String[] words = content.split("\\W+");

List<String> palindromes = Arrays.stream(words)

.filter(word -> word.length() > 1 && word.equalsIgnoreCase(new StringBuilder(word).reverse().toString()))

.collect(Collectors.toList());

ByteBuffer outputBuffer = StandardCharsets.UTF_8.encode(String.join("\n", palindromes));

outChannel.write(outputBuffer);

}

System.out.println("Palindromes extracted successfully!");

}

}

//class NIOFileProcessing {

//

// /**

// * **1) Reverse Content of a Large File (NIO-based version)**

// * Reads a large file line by line using FileChannel, reverses each line,

// * and writes it to another file using FileChannel.

// */

// public static void reverseFileContent(String inputFile, String outputFile) throws IOException {

// List<String> lines = Files.readAllLines(Paths.get(inputFile), StandardCharsets.UTF_8);

// Collections.reverse(lines);

// Files.write(Paths.get(outputFile), lines, StandardCharsets.UTF_8);

// System.out.println("File reversed successfully!");

// }

//

// /**

// * **2) Find and Replace Words in a File (NIO-based version)**

// * Reads a file, replaces occurrences of a word with another,

// * and writes to a new file using FileChannel and ByteBuffer.

// */

// public static void findAndReplace(String inputFile, String outputFile, String target, String replacement) throws IOException {

// Path path = Paths.get(inputFile);

// String content = new String(Files.readAllBytes(path), StandardCharsets.UTF_8);

// content = content.replaceAll(target, replacement);

// Files.write(Paths.get(outputFile), content.getBytes(StandardCharsets.UTF_8));

// System.out.println("Find and replace completed!");

// }

//

// /**

// * **3) Custom CSV Parser (NIO-based version)**

// * Reads a CSV file using FileChannel, processes each line to extract values,

// * and writes formatted output using FileChannel.

// */

// public static void parseCSV(String inputFile, String outputFile) throws IOException {

// List<String> lines = Files.readAllLines(Paths.get(inputFile), StandardCharsets.UTF_8);

// List<String> parsedLines = new ArrayList<>();

//

// for (String line : lines) {

// String[] values = line.split(",(?=([^\"]*\"[^\"]*\")*[^\"]*$)"); // Handles quoted values

// parsedLines.add(Arrays.toString(values));

// }

//

// Files.write(Paths.get(outputFile), parsedLines, StandardCharsets.UTF_8);

// System.out.println("CSV Parsing completed!");

// }

//

// /**

// * **4) Word Frequency Counter in Large File (NIO-based version)**

// * Reads a file using FileChannel, counts word frequency (ignoring case),

// * and writes results to another file.

// */

// public static void countWordFrequency(String inputFile, String outputFile) throws IOException {

// Path path = Paths.get(inputFile);

// String content = new String(Files.readAllBytes(path), StandardCharsets.UTF_8).toLowerCase();

// String[] words = content.split("\\W+");

//

// Map<String, Integer> frequencyMap = new HashMap<>();

// for (String word : words) {

// frequencyMap.put(word, frequencyMap.getOrDefault(word, 0) + 1);

// }

//

// List<String> result = frequencyMap.entrySet().stream()

// .map(entry -> entry.getKey() + " : " + entry.getValue())

// .collect(Collectors.toList());

//

// Files.write(Paths.get(outputFile), result, StandardCharsets.UTF_8);

// System.out.println("Word frequency count completed!");

// }

//

// /**

// * **5) Extract Palindromes from a File (NIO-based version)**

// * Reads a file character by character using FileChannel, extracts palindrome words,

// * and writes them to another file.

// */

// public static void extractPalindromes(String inputFile, String outputFile) throws IOException {

// Path path = Paths.get(inputFile);

// String content = new String(Files.readAllBytes(path), StandardCharsets.UTF_8);

// String[] words = content.split("\\W+");

//

// List<String> palindromes = Arrays.stream(words)

// .filter(word -> word.length() > 1 && word.equalsIgnoreCase(new StringBuilder(word).reverse().toString()))

// .collect(Collectors.toList());

//

// Files.write(Paths.get(outputFile), palindromes, StandardCharsets.UTF_8);

// System.out.println("Palindromes extracted successfully!");

// }

//

//}