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POIs this code a thread-safe one?
 

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    <p>I want to process a flow of client requests. Each request has its special type. First I need to initialize some data for that type, and after this I can start processing the requests. When the client type comes for the first time, I just initialize the corresponding data. After this all the following requests of that type are processed using that data. </p> <p>I need to do this in a thread-safe manner.</p> <p>Here is a code I have written. Is it thread-safe?</p> <pre><code>public class Test { private static Map&lt;Integer, Object&gt; clientTypesInitiated = new ConcurrentHashMap&lt;Integer, Object&gt;(); /* to process client request we need to create corresponding client type data. on the first signal we create that data, on the second - we process the request*/ void onClientRequestReceived(int clientTypeIndex) { if (clientTypesInitiated.put(clientTypeIndex, "") == null) { //new client type index arrived, this type was never processed //process data for that client type and put it into the map of types Object clientTypeData = createClientTypeData(clientTypeIndex); clientTypesInitiated.put(clientTypeIndex, clientTypeData); } else { //already existing index - we already have results and we can use them processClientUsingClientTypeData(clientTypesInitiated.get(clientTypeIndex)); } } Object createClientTypeData(int clientIndex) {return new Object();} void processClientUsingClientTypeData(Object clientTypeData) {} } </code></pre> <p>From one hand, ConcurrentHashMap cannot produce map.put(A,B) == null two times for the same A. From the other hand, the assignment and comparisson operation is not thread-safe. </p> <p>So is this code is ok? If not, how can I fix it?</p> <p>UPDATE: I have accepted the answer of Martin Serrano because his code is thread-safe and it is not prone to double initialization issue. But I would like to note, that I have not found any isssues with my version, posted as an answer below, and my version does not require synchronization.</p>
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