[Ch15b] Even simpler concurrent readers example

import java.time.LocalDateTime;

import java.time.format.FormatStyle;

import java.util.List;

import java.util.concurrent.CopyOnWriteArrayList;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.TimeUnit;

import java.util.*;

import java.util.concurrent.*;

import static java.time.format.DateTimeFormatter.ofLocalizedTime;

public class LotsOfReaders {

public class ConcurrentReaders {

  public static void main(String[] args) throws InterruptedException {

    List<Chat> chatHistory = new CopyOnWriteArrayList<>();

    List<Chat> chatHistory = new ArrayList<>();

    ExecutorService executor = Executors.newFixedThreadPool(3);

    for (int i = 0; i < 5; i++) {

      executor.execute(() -> chatHistory.add(new Chat("Hi there!")));

      executor.execute(() -> printChatHistory("Reader 1", chatHistory));

      executor.execute(() -> printChatHistory("Reader 2", chatHistory));

      executor.execute(() -> System.out.println(chatHistory));

      executor.execute(() -> System.out.println(chatHistory));

    }

    executor.shutdown();

    executor.awaitTermination(1, TimeUnit.MINUTES);

  }

  private static void printChatHistory(String name, List<Chat> chatHistory) {

    for (Chat chat : chatHistory) {

      System.out.println(name + " read: " + chat);

    }

  }

}

class Chat {

final class Chat {

  private final String message;

  private final LocalDateTime timestamp;