gistfile1.java

// we want a return value here.
int i = wrap(new Callable<Integer>() {
  public Integer call() {
    return 42;
  }
})

// if we don't have a return value, we're forced to return null
wrap(new Callable<Void>() {
  public Void call() {
    // do stuff
    return null;
  }
})

// ah, much better.
wrap(Executors.callable(new Runnable() {
  public void run() {
    // do stuff
  }
}))