Created
April 20, 2023 13:24
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| import java.util.ArrayList; | |
| import java.util.List; | |
| import java.util.Random; | |
| import java.util.concurrent.ConcurrentHashMap; | |
| import java.util.concurrent.Executor; | |
| import java.util.concurrent.ExecutorService; | |
| import java.util.concurrent.Executors; | |
| import java.util.function.BiFunction; | |
| import java.util.function.Function; | |
| public class Main { | |
| private static final Random random = new Random(); | |
| public static void main(String[] args) throws InterruptedException { | |
| ExecutorService executor = Executors.newSingleThreadExecutor(); | |
| CommandExecutor commandExecutor = new CommandExecutorImpl(executor, Main::handleUrlSync); | |
| for (int i = 0; i < 100; ++i) { | |
| String url = "url" + (random.nextInt(10) + 1); | |
| commandExecutor.requestAsync(url, Main::print); | |
| Thread.sleep(random.nextInt(200)); | |
| } | |
| executor.shutdown(); | |
| } | |
| private static String handleUrlSync(String url) { | |
| long start = System.currentTimeMillis(); | |
| try { | |
| Thread.sleep(random.nextInt(2000)); | |
| } catch (InterruptedException ex) { | |
| throw new RuntimeException(ex); | |
| } | |
| long end = System.currentTimeMillis(); | |
| return start + " .. " + end; | |
| } | |
| private static Void print(String key, String value) { | |
| System.out.println(key + " > " + value); | |
| return null; | |
| } | |
| interface CommandExecutor { | |
| void requestAsync(String url, BiFunction<String, String, Void> callback); | |
| } | |
| static class CommandExecutorImpl implements CommandExecutor { | |
| private final Executor executor; | |
| private final Function<String, String> urlHandler; | |
| private final ConcurrentHashMap<String, List<BiFunction<String, String, Void>>> callbacks = new ConcurrentHashMap<>(); | |
| public CommandExecutorImpl(Executor executor, Function<String, String> urlHandler) { | |
| this.executor = executor; | |
| this.urlHandler = urlHandler; | |
| } | |
| @Override | |
| public void requestAsync(String url, BiFunction<String, String, Void> callback) { | |
| List<BiFunction<String, String, Void>> list = callbacks.computeIfAbsent(url, $ -> new ArrayList<>()); | |
| synchronized (list) { | |
| list.add(callback); | |
| if (list.size() == 1) { | |
| executor.execute(() -> handleUrl(url, list)); | |
| } | |
| } | |
| } | |
| @SuppressWarnings("SynchronizationOnLocalVariableOrMethodParameter") | |
| private void handleUrl(String url, List<BiFunction<String, String, Void>> list) { | |
| String response = urlHandler.apply(url); | |
| if (callbacks.remove(url) != list) { | |
| throw new IllegalStateException(); | |
| } | |
| synchronized (list) { | |
| for (BiFunction<String, String, Void> callback : list) { | |
| callback.apply(url, response); | |
| } | |
| } | |
| } | |
| } | |
| } |
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