@Test
    public void howToAddElementsToSet() {
        Table table = dynamo.getTable(TABLE_NAME);
        // Add a set of phone numbers to the attribute "phone"
        final String phoneNumber1 = "123-456-7890";
        table.updateItem(HASH_KEY, FIRST_CUSTOMER_ID, RANGE_KEY, ADDRESS_TYPE_WORK,
            new AttributeUpdate("phone").put(new FluentHashSet<String>(phoneNumber1)));
        GetItemOutcome outcome = table.getItemOutcome(new GetItemSpec()
            .withPrimaryKey(HASH_KEY, FIRST_CUSTOMER_ID, RANGE_KEY, ADDRESS_TYPE_WORK)
            .withConsistentRead(true)
        );
        Item item = outcome.getItem();
        Set<String> phoneNumbers = item.getStringSet("phone");
        assertTrue(1 == phoneNumbers.size());
        System.out.println(phoneNumbers);

        // Add a 2nd phone number to the set
        final String phoneNumber2 = "987-654-3210";
        table.updateItem(HASH_KEY, FIRST_CUSTOMER_ID, RANGE_KEY, ADDRESS_TYPE_WORK,
            new AttributeUpdate("phone").addElements(phoneNumber2));
        outcome = table.getItemOutcome(new GetItemSpec()
            .withPrimaryKey(HASH_KEY, FIRST_CUSTOMER_ID, RANGE_KEY, ADDRESS_TYPE_WORK)
            .withConsistentRead(true));
        item = outcome.getItem();
        phoneNumbers = item.getStringSet("phone");
        System.out.println(phoneNumbers);
        assertTrue(2== phoneNumbers.size());

        // removes the 2nd phone number from the set
        table.updateItem(HASH_KEY, FIRST_CUSTOMER_ID, RANGE_KEY, ADDRESS_TYPE_WORK,
            new AttributeUpdate("phone").removeElements(phoneNumber2));
        outcome = table.getItemOutcome(new GetItemSpec()
            .withPrimaryKey(HASH_KEY, FIRST_CUSTOMER_ID, RANGE_KEY, ADDRESS_TYPE_WORK)
            .withConsistentRead(true));
        item = outcome.getItem();
        phoneNumbers = item.getStringSet("phone");
        System.out.println(phoneNumbers);
        assertTrue(1 == phoneNumbers.size());

        // deletes the phone attribute
        table.updateItem(HASH_KEY, FIRST_CUSTOMER_ID, RANGE_KEY, ADDRESS_TYPE_WORK, 
                new AttributeUpdate("phone").delete());
        outcome = table.getItemOutcome(new GetItemSpec()
            .withPrimaryKey(HASH_KEY, FIRST_CUSTOMER_ID, RANGE_KEY, ADDRESS_TYPE_WORK)
            .withConsistentRead(true));
        item = outcome.getItem();
        phoneNumbers = item.getStringSet("phone");
        assertNull(phoneNumbers);
    }
Sample code to update items to a dynamo table.
src/samples/AmazonDynamoDBDocumentAPI/quick-start/com/amazonaws/services/dynamodbv2/document/quickstart/F_UpdateItemTest.java