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    <p>There are number of ways to do this. A better solution would be to switch and use <code>ExecutorService</code> instead of forking the threads yourself. You then can then implement <code>Callable&lt;Map&gt;</code> (instead of <code>Runnable</code>) in your <code>SecondClass</code> and return the maps that each of the jobs create.</p> <p>Something like:</p> <pre><code>// create a thread pool with as many workers as there are jobs ExecutorService threadPool = Executors.newCachedThreadPool(); List&lt;Future&lt;Map&lt;String, Integer&gt;&gt;&gt; futures = new ArrayList&lt;Future&lt;Map&lt;String, Integer&gt;&gt;&gt;(); futures.add(threadPool.submit(new SecondClass(s1))); futures.add(threadPool.submit(new SecondClass(s2))); futures.add(threadPool.submit(new SecondClass(s3))); futures.add(threadPool.submit(new SecondClass(s4))); // once we have submitted all jobs to the thread pool, it should be shutdown threadPool.shutdown(); ... Map&lt;String, Integer&gt; all = new HashMap&lt;String, Integer&gt;(); for (Future&lt;Map&lt;String, Integer&gt;&gt; future : futures) { // future.get() throws an exception if your call method throws all.putAll(future.get()); } </code></pre> <p>So then your <code>SecondClass</code> implements <code>Callable</code>:</p> <pre><code>public Map&lt;String, Integer&gt; call() { ... return map; } </code></pre> <p>Some other mechanisms that you could use include:</p> <ul> <li>Using a shared <code>ConcurrentHashMap</code> that was passed in (better) or <code>static</code> (not as good)</li> <li>Have your threads put their results on a <code>BlockingQueue</code> when they are done</li> <li>Join with the threads and then call a method on the class that gets the <code>Map</code> that was created.</li> </ul>
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    1. POHow do you return one instance of a variable that has been edited in 4 different Threads?
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    1. COThanks, Gray! I am a little confused with your above code in relation to mine though (not your fault). The thread pool holds a certain amount of threads (10 it seems) and these are then executed and the program waits until they are finished, right? So how would I get multiple threads to do the same job but with different _String_ variables whilst all the time adding to the same HashMap? Create list of jobs to do and execute the entire pool rather than threads individually and wait until they finish? I'm sorry, I will go ahead and read about _ExecutorService_ but any extra pointers?
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    2. COoh wait, I jumped the gun and posted before your edit. That makes more sense to me now, thank you. Would the above be done in **FirstClass** and then in my **SecondClass**, I would implement _Callable_ rather than _Runnable_ ?
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    3. COThe thread-pool would be created in `FirstClass`. The `SecondClass` would implement `Callable` @UserBruiser.
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