/**
  * Once the servers signature over the refund transaction has been received and provided using
  * {@link PaymentChannelClientState#provideRefundSignature(byte[])} then this method can be called
  * to receive the now valid and broadcastable refund transaction.
  */
 public synchronized Transaction getCompletedRefundTransaction() {
   checkState(state.compareTo(State.WAITING_FOR_SIGNED_REFUND) > 0);
   return refundTx;
 }
 /**
  * Returns the fees that will be paid if the refund transaction has to be claimed because the
  * server failed to settle the channel properly. May only be called after {@link
  * PaymentChannelClientState#initiate()}
  */
 public synchronized Coin getRefundTxFees() {
   checkState(state.compareTo(State.NEW) > 0);
   return refundFees;
 }