guava/src/com/google/common/util/concurrent/Callables.java
public static <T> Callable<T> returning(final @Nullable T value) {
    return new Callable<T>() {
      @Override
      public T call() {
        return value;
      }
    };
  }
public static <T> Callable<T> returning(final @Nullable T value) {
    return new Callable<T>() {
      @Override
      public T call() {
        return value;
      }
    };
  }
Creates a {@code Callable} which immediately returns a preset value each time it is called.