title: NullPointerException when attempting ConcurrentHashMap.get()
body: <p>I have the following code:</p>
  
  <pre><code>public class MyEvent implements org.apache.camel.Processor
  {
      static private final Map&lt;Long, String&gt; obj = new ConcurrentHashMap&lt;Long, String&gt;();
  
      @PostConstruct
      public void postConstruct() 
      {
          for (Object object : cacheList) 
          {
              obj.put(object.getId(), object.getName());
          }
      }
  
      @Override
      public void process(Exchange exchange) throws Exception 
      {
          synchronized (obj) 
          {
              String value = obj.get(number);
          }
      }
  }
  </code></pre>
  
  <p>Sometimes when starting, I have a <code>NullPointerException</code> in this line:</p>
  
  <pre><code>String value = obj.get(number);
  </code></pre>
  
  <p>My question is: Why do I get this error and how can I fix it?</p>
  
  <p>Java version 1.6.0_32</p>