title: Java Multithread Application uses only one Core
body: <p>I have a problem with my JVM Running on a CentOS 6.0 with openJDK 1.7.0_51 64Bit.
  My System is a 4-Core System with 8GB Ram.</p>
  
  <p>I'm running a Java multithread application that I wrote myself. It's supposed to insert tons of Data into a NoSQL Database. 
  For that, I'm spawning 4 threads, using a "CachedThreadPoolExecutor" from java.concurrent.Executors.</p>
  
  <p>I instantiate 4 Workers that implement the "Runnable" Interface. Afterwards I execute the Thread using the threadpool. Here's my code:</p>
  
  <pre><code> public void startDataPump(int numberOfWorkers){
     //class "DataPump" implements runnable
     for (int i = 0; i &lt; numberOfWorkers; i++){
        DataPump pump = new DataPump();
        //"workerList" contains all workers and is a simple arrayList to keep track of the workers
        workerList.add(pump);
        //"workers" is the thradpool that has been 
        //initialized earlier with "Executors.newCachedThreadPool()
        workers.execute(pump);
     }
   }
  </code></pre>
  
  <p>When running this, using a parameter of 4, it will spawn 4 Threads in the Threadpool. I assumed that the JVM or my OS would be smart enough to schedule these threads on all of my cores. 
  HOWEVER, only one core of my cpu is working at 100%,the others remain almost idle.</p>
  
  <p>Am I doing anything wrong in my code or is this a JVM/OS problem. If so, is there anything I can do about that?
  Running this application on only 1 core is extremeley slowing down the whole app.</p>
  
  <p>Help is greatly appreciated :)</p>