Does JDBC's executeBatch() execute statements in parallel or one after the other

I want to delete entries from multiple tables in a postgreSQL DB.
The tables have foreign key constraints, so I need to delete them in particular order only (otherwise delete will fail).

I am thinking of adding them to a batch and running executeBatch()

I understand that executeBatch submits all the statements together to driver but how are statements executed? Is the order of deletion will be maintained as per order of adding to the batch? I can't find it mentioned in API doc

The JDBC 4.3 specification explicitly specifies the behaviour of a batch execution in section 14.1.2 Successful Execution:

> Batch commands are executed serially (at least logically) in the order
> in which they were added to the batch.

and

> The entries in the array are ordered according to the order in which
> the commands were processed (which, again, is the same as the order in
> which the commands were originally added to the batch).

The "at least logically" gives databases some leeway to reorder things as an optimization, as long as the resulting behaviour is the same as if the batch was executed in the specified order. Execution in-order is also necessary to ensure the returned update counts match, and for exception behaviour.

They are executed in order.

The purpose of "batching" is to collect the SQL statements and transmit them as a block, a sequence of statements, in order to reduce the network overhead of communicating with the database server.

A full "send SQL, wait for response" takes time, so by sending multiple requests together, a lot of waiting time can be eliminated.