Java Project: Tiny Quote Server

A ConcurrentHashMap holds three quotes by number. The program looks up number 2 and a missing number.

import java.util.concurrent.ConcurrentHashMap;

public class Main {
  public static void main(String[] args) {
    ConcurrentHashMap<Integer, String> quotes = new ConcurrentHashMap<>();
    quotes.put(1, "Small steps every day.");
    quotes.put(2, "Make it work, then make it clear.");
    quotes.put(3, "Programs are read more than written.");
    System.out.println("Quote 2: " + quotes.getOrDefault(2, "Unknown quote"));
    System.out.println("Quote 9: " + quotes.getOrDefault(9, "Unknown quote"));
  }
}

A fixed pool of two threads runs four small tasks. Each task adds one to an AtomicInteger, and the main thread prints the final count.

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class Main {
  public static void main(String[] args) throws Exception {
    ExecutorService pool = Executors.newFixedThreadPool(2);
    AtomicInteger count = new AtomicInteger();
    for (int i = 0; i < 4; i++) {
      pool.submit(() -> {
        count.incrementAndGet();
      });
    }
    pool.shutdown();
    pool.awaitTermination(10, TimeUnit.SECONDS);
    System.out.println("Count: " + count.get());
  }
}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;

public class Main {
  public static void main(String[] args) throws Exception {
    ConcurrentHashMap<Integer, String> quotes = new ConcurrentHashMap<>();
    quotes.put(1, "Small steps every day.");
    quotes.put(2, "Make it work, then make it clear.");
    quotes.put(3, "Programs are read more than written.");
    String[] requests = new String[4];
    AtomicInteger ticket = new AtomicInteger();
    AtomicInteger served = new AtomicInteger();
    CountDownLatch done = new CountDownLatch(4);
    ExecutorService pool = Executors.newFixedThreadPool(2);
    try (ServerSocket server = new ServerSocket(0)) {
      System.out.println("PORT " + server.getLocalPort());
      for (int i = 0; i < 4; i++) {
        Socket socket = server.accept();
        int slot = ticket.getAndIncrement();
        pool.submit(() -> {
          try (socket;
               BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), StandardCharsets.UTF_8));
               PrintWriter writer = new PrintWriter(socket.getOutputStream(), true, StandardCharsets.UTF_8)) {
            String line = reader.readLine();
            requests[slot] = line;
            writer.println(lookup(quotes, line));
            served.incrementAndGet();
          } catch (Exception e) {
            System.out.println("Handler error: " + e);
          } finally {
            done.countDown();
          }
        });
      }
      done.await();
    } finally {
      pool.shutdown();
    }
    for (String request : requests) {
      System.out.println("Request: " + request);
    }
    System.out.println("Requests served: " + served.get());
  }

  static String lookup(ConcurrentHashMap<Integer, String> quotes, String line) {
    if (line != null && line.startsWith("quote ")) {
      try {
        int number = Integer.parseInt(line.substring(6).trim());
        return quotes.getOrDefault(number, "Unknown quote");
      } catch (NumberFormatException e) {
        return "Unknown quote";
      }
    }
    return "Unknown quote";
  }
}