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    <p>You should use <code>Futures</code> and <code>Callables</code> if you want to wait compute something in asynchronous and wait for the results.</p> <p>Implement <code>Callable</code> interface:</p> <pre><code>class MoveMessages implements Callable&lt;Boolean&gt; { @Override public Boolean call() throws Exception { boolean success = true; // Your implementation here return success; } </code></pre> <p>}</p> <p>And next submit it to Executor and retrieve <code>Future</code>, invoking <code>get()</code> on Future you will wait until computation of Callable is done. </p> <pre><code>ExecutorService executor = Executors.newFixedThreadPool(5); MoveMessages moveMessages = new MoveMessages(); Future&lt;Boolean&gt; submit = executor.submit(moveMessages); Boolean integer = submit.get(); // Will wait until task is finished executor.shutdown(); </code></pre> <p>Of course you can submit more task gets all to list and wait until all will finish.</p> <p><strong>Edit:</strong></p> <p>OK, first you say that you need to wait until all messages are moved, so one way for that case is to use <code>Future</code> and <code>callable</code> with <code>ExecutorService</code>. Using <code>ExecutorService</code> you do not need to create and start lots of new threads. Remember creating new thread generate costs. In your code you create 4 new threads for each sender, using <code>ExecutorService</code> you create only fixed number of threads and reuse them for each Sender. Here is your example using <code>Executors</code> and <code>Futures</code>, note that ExecutorService is created once for invoking <code>moveMessagesToFolders</code>:</p> <pre><code>private static ExecutorService executor private static void moveMessagesToFolders(List&lt;Message&gt; listMessages, Store store, Set&lt;String&gt; setSender) throws MessagingException { executor = Executors.newFixedThreadPool(4); HashMap&lt;String, List&lt;Message&gt;&gt; mapMessages = separeteMessagesBySender(listMessages, setSender); for (Map.Entry&lt;String, List&lt;Message&gt;&gt; mapMessage : mapMessages.entrySet()) { Message[] messageArray = mapMessage.getValue().toArray(new Message[mapMessage.getValue().size()]); moveMessagesThread(messageArray, mapMessage, store); } executor.shutdown(); } private static void moveMessagesThread(Message[] messageArray, Map.Entry&lt;String, List&lt;Message&gt;&gt; mapMessage, Store store) { List&lt;Future&lt;Boolean&gt;&gt; futures = createMovimentSetThread(messageArray, mapMessage, store); for (Future&lt;Boolean&gt; future : futures) { try { Boolean success = future.get(); // Will wait to accomplished all submited Callables if(!success) { // Check if all submited callables end succesulfy throw new RuntimeException("Something goes wrong while moving messages"); } } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } } } private static List&lt;Future&lt;Boolean&gt;&gt; createMovimentSetThread(Message[] messageArray, Map.Entry&lt;String, List&lt;Message&gt;&gt; mapMessage, Store store) { int [] threadIndexs = MathUtil.generateIndex(messageArray); List&lt;Future&lt;Boolean&gt;&gt; futures = new ArrayList&lt;&gt;(); for (int i = 0; i &lt; threadIndexs.length; i++) { Future&lt;Boolean&gt; submit = executor.submit(new ThreadMoveMessages(messageArray, mapMessage, store, threadIndexs[i])); futures.add(submit); } return futures; } </code></pre> <p>According to your comments, that you split array to smaller pieces using Fork/Join framework may be a better solution. Look in google for some more information. Some links:</p> <ul> <li><a href="http://docs.oracle.com/javase/tutorial/essential/concurrency/forkjoin.html" rel="nofollow noreferrer">http://docs.oracle.com/javase/tutorial/essential/concurrency/forkjoin.html</a></li> <li><a href="https://stackoverflow.com/questions/3524634/java-7-fork-join-framework">Java 7: Fork/Join Framework</a></li> </ul>
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    1. POHaving problemns using threads to copy emails to folder in javamail
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    1. COOk, but I don´t need to create 5 `instances` of the `moveMessages` class? I put the code in the question Because i share one array in other arrays smallers to make easier the job
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      1. USDiego Macario
    2. COYou can use only one thread or more to accomplished all tasks. 5 it was only for example. Read about `Executors` you will find that you can maintain only one `ExecutorSerive` for entire application so you will only submit callables to it for different invocation of `moveMessagesToFolders`. Look on this site [link](http://www.vogella.com/articles/JavaConcurrency/article.html#threadpools)
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      1. USMarcin Wagner
    3. COfor you understand, I have a hahsmap with the email senders and a list of messages, i get this list and move the messages to the folders, but I want to increase the process of move message because it´s slow
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