[Ch15b] Using CopyOnWriteArrayList to fix reader code

import java.time.LocalDateTime;

import java.time.format.FormatStyle;

import java.util.ArrayList;

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 static java.time.format.DateTimeFormatter.ofLocalizedTime;

public class LotsOfReaders {

  public static void main(String[] args) {

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

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

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

    ExecutorService executor = Executors.newFixedThreadPool(3);

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

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

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

    }

    executor.shutdown();

    executor.awaitTermination(1, TimeUnit.MINUTES);

  }

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