How to convert List<Object> into comma separated String

Question

I am getting list of Address objects from the DB call.

ArrayList<Address> addresses = new ArrayList<>(); 

Each Address has an int addressId property.

I am writing an update query where in the IN clause I am sending this whole list of Address objects and I am getting ibatis TypeException. How can I convert List<Address> to a comma separated string which can be sent to update query?

My update query looks like:::

Update tablename set postcode = #{postCode} where id in #{addressID}. 

Answer 1

Using Java 8 you could do it in one line:

String addressID = addresses            .stream()            .map(a -> String.valueOf(a.addressId))            .collect(Collectors.joining(",")); 

Answer 2

for converting to comma seperated String use something like this:

String commaSeparatedStr = addresses         .stream()         .map(String::valueOf)         .collect(Collectors.joining(","));