You have a syntax error with your case expression, I would guess you want
SET NAME = CASE ID WHEN 1 THEN 'NAME1'
WHEN 2 THEN 'NAME2' end
where ID IN (1, 2);
If you want to handle a large amount of different keys and values then you could use one statement with bulk binds (array binds), the coding of this will depend on the driver you are using but it will look something like
statement='update users set name = :name where id = :id';
binds = array of names, array of ids;
In general, this will perform similarly to the previous approach. The previous approach is favourable if this is a one off.
You could also load a staging table with
id,name pairs from a flat file with SQL*Loader and then use a merge statement
merge into users u
using staging_users su
on (u.id = su.id)
when matched then update
set u.name = su.name