Making coordinated changes to multiple items with Amazon DynamoDB transactions

private static void createTable(String tableName) {
        try {
        	// Create a table with a primary hash key named 'Id', which holds a string
            CreateTableRequest createTableRequest = new CreateTableRequest().withTableName(tableName)
                .withKeySchema(new KeySchemaElement().withAttributeName("Id").withKeyType(KeyType.HASH))
                .withAttributeDefinitions(new AttributeDefinition().withAttributeName("Id").withAttributeType(ScalarAttributeType.S))
                .withProvisionedThroughput(new ProvisionedThroughput().withReadCapacityUnits(1L).withWriteCapacityUnits(1L));

            // Create table if it does not exist yet
            TableUtils.createTableIfNotExists(dynamoDB, createTableRequest);

            // wait for the table to move into ACTIVE state
        	TableUtils.waitUntilActive(dynamoDB, tableName);
        	
            // Describe our new table
            DescribeTableRequest describeTableRequest = new DescribeTableRequest().withTableName(tableName);
            TableDescription tableDescription = dynamoDB.describeTable(describeTableRequest).getTable();
            System.out.println("Table Created Successfully. Table Description: " + tableDescription);
        	
		} catch (InterruptedException e) {
        	System.out.println("Occupied thread is interrupted");
		}
    }

    private static void createReservation() {
    	
        // Create guest item
    	HashMap<String, AttributeValue> guestItem = new HashMap<String, AttributeValue>();
    	guestItem.put("Id", new AttributeValue("John"));
    	guestItem.put("ActiveReservations", new AttributeValue("500"));
    	
        // Create room item
    	HashMap<String, AttributeValue> roomItem = new HashMap<String, AttributeValue>();
    	roomItem.put("Id", new AttributeValue("R20014"));
    	roomItem.put("RoomStatus", new AttributeValue("FREE"));
        
        // Create reservation item
    	HashMap<String, AttributeValue> reservationItem = new HashMap<String, AttributeValue>();
    	reservationItem.put("Id", new AttributeValue("500"));
    	reservationItem.put("GuestId", new AttributeValue("John"));
    	reservationItem.put("ReservationStatus", new AttributeValue("PENDING"));

        Put createGuest = new Put().withTableName(TABLE_NAME).withItem(guestItem);
        Put createRoom = new Put().withTableName(TABLE_NAME).withItem(roomItem);
        Put createReservation = new Put().withTableName(TABLE_NAME).withItem(reservationItem);

        Collection<TransactWriteItem> actions = Arrays.asList(
        		new TransactWriteItem().withPut(createGuest),
                new TransactWriteItem().withPut(createRoom),
                new TransactWriteItem().withPut(createReservation));
        
        TransactWriteItemsRequest createReservationTransaction = new TransactWriteItemsRequest()
                .withTransactItems(actions)
                .withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL);

	    // Execute the transaction and process the result.
		// The following code snippet illustrates how to execute the actions defined previously as a single all-or-nothing operation
        dynamoDB.transactWriteItems(createReservationTransaction);
        System.out.println("Create Reservation transaction is successful");
    }

    private static void checkIn() {
    	
    	//Create updateGuest object
    	HashMap<String, AttributeValue> guestItemKey = new HashMap<String, AttributeValue>();
    	guestItemKey.put("Id", new AttributeValue("John"));
    	
    	HashMap<String, AttributeValue> guestExpressionAttributeValues = new HashMap<String, AttributeValue>();
    	guestExpressionAttributeValues.put(":occupies_rooms", new AttributeValue("R20014"));
    	
    	Update updateGuest = new Update()
    			.withTableName(TABLE_NAME)
    			.withKey(guestItemKey)
    			.withUpdateExpression("SET OccupiesRooms = :occupies_rooms")
    			.withExpressionAttributeValues(guestExpressionAttributeValues);

    	
    	//Create updateRoom object
    	HashMap<String, AttributeValue> roomItemKey = new HashMap<String, AttributeValue>();
    	roomItemKey.put("Id", new AttributeValue("R20014"));
    	
    	HashMap<String, AttributeValue> roomExpressionAttributeValues = new HashMap<String, AttributeValue>();
    	roomExpressionAttributeValues.put(":room_status", new AttributeValue("OCCUPIED"));
    	roomExpressionAttributeValues.put(":rented_to_reservation", new AttributeValue("500"));
    	
    	Update updateRoom = new Update()
    			.withTableName(TABLE_NAME)
    			.withKey(roomItemKey)
    			.withUpdateExpression("SET RoomStatus = :room_status, RentedToReservation = :rented_to_reservation")
    			.withExpressionAttributeValues(roomExpressionAttributeValues);

    	//Create updateReservation object
    	HashMap<String, AttributeValue> reservationItemKey = new HashMap<String, AttributeValue>();
    	reservationItemKey.put("Id", new AttributeValue("500"));
    	
    	HashMap<String, AttributeValue> reservationExpressionAttributeValues = new HashMap<String, AttributeValue>();
    	reservationExpressionAttributeValues.put(":reservation_status", new AttributeValue("FULLFILLED"));
    	reservationExpressionAttributeValues.put(":fullfilled_by_room", new AttributeValue("R20014"));
    	
    	Update updateReservation = new Update()
    			.withTableName(TABLE_NAME)
    			.withKey(reservationItemKey)
    			.withUpdateExpression("SET ReservationStatus = :reservation_status, FullfilledByRoom = :fullfilled_by_room")
    			.withExpressionAttributeValues(reservationExpressionAttributeValues);
    	
    	//Execute transaction
    	Collection<TransactWriteItem> actions = Arrays.asList(
        		new TransactWriteItem().withUpdate(updateGuest),
                new TransactWriteItem().withUpdate(updateRoom),
                new TransactWriteItem().withUpdate(updateReservation));
        
        TransactWriteItemsRequest createReservationTransaction = new TransactWriteItemsRequest()
                .withTransactItems(actions)
                .withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL);

        dynamoDB.transactWriteItems(createReservationTransaction);
        System.out.println("Check-in transaction is successful");
    	
    }

    private static void checkOut() {
    	//Create updateGuest object
    	HashMap<String, AttributeValue> guestItemKey = new HashMap<String, AttributeValue>();
    	guestItemKey.put("Id", new AttributeValue("John"));
    	
    	Update updateGuest = new Update()
    			.withTableName(TABLE_NAME)
    			.withKey(guestItemKey)
    			.withUpdateExpression("REMOVE OccupiesRooms, ActiveReservations");
    	//Since there is no value in the attribute, it is removed
    	
    	//Create updateRoom object
    	HashMap<String, AttributeValue> roomItemKey = new HashMap<String, AttributeValue>();
    	roomItemKey.put("Id", new AttributeValue("R20014"));
    	
    	HashMap<String, AttributeValue> roomExpressionAttributeValues = new HashMap<String, AttributeValue>();
    	roomExpressionAttributeValues.put(":room_status", new AttributeValue("FREE"));
    	
    	Update updateRoom = new Update()
    			.withTableName(TABLE_NAME)
    			.withKey(roomItemKey)
    			.withUpdateExpression("SET RoomStatus = :room_status REMOVE RentedToReservation") //Since there is no value in the attribute, it is removed
    			.withExpressionAttributeValues(roomExpressionAttributeValues);
    	
    	//Create updateReservation object
    	HashMap<String, AttributeValue> reservationItemKey = new HashMap<String, AttributeValue>();
    	reservationItemKey.put("Id", new AttributeValue("500"));
    	
    	HashMap<String, AttributeValue> reservationExpressionAttributeValues = new HashMap<String, AttributeValue>();
    	reservationExpressionAttributeValues.put(":reservation_status", new AttributeValue("CLOSED"));
    	
    	Update updateReservation = new Update()
    			.withTableName(TABLE_NAME)
    			.withKey(reservationItemKey)
    			.withUpdateExpression("SET ReservationStatus = :reservation_status")
    			.withExpressionAttributeValues(reservationExpressionAttributeValues);
    	
    	//Execute transaction
    	Collection<TransactWriteItem> actions = Arrays.asList(
        		new TransactWriteItem().withUpdate(updateGuest),
                new TransactWriteItem().withUpdate(updateRoom),
                new TransactWriteItem().withUpdate(updateReservation));
        
        TransactWriteItemsRequest createReservationTransaction = new TransactWriteItemsRequest()
                .withTransactItems(actions)
                .withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL);

        dynamoDB.transactWriteItems(createReservationTransaction);
        System.out.println("Check-out transaction is successful");
    }