C#

public class ManagerClass {
  private List<BeanType> beans = new List<BeanType>();
  private static Object lockObj = new Object();
  private static readonly int MAX_THREADS = 5;

  public List<BeanType> getBeans() {
    string[] keys = null;

    keys = getKeys();
    ThreadPool.SetMaxThreads(MAX_THREADS, MAX_THREADS);

    foreach (string key in keys) {
      ThreadPool.QueueUserWorkItem(new WaitCallback(getValueThreaded), key);
    }
    // Assuming 10000 is enough time for the threads to finish.
    Thread.Sleep(10000);
    Console.WriteLine(beans.Capacity);
    return beans;
  }

  public void getValueThreaded(object obj) {
    string key = (string)obj;
    string value = getValue(key);

    lock(lockObj) {
      beans.Add(new BeanType(key, value));
    }
  }
}