Find and exists methods in ax 2012

find :-
All tables should have at least one find method that selects and returns one record
from the table that matches the unique index specified by the input parameters.
The last input parameter in a find method should be a Boolean variable called
'forupdate' or 'update' that is defaulted to false. When it is set to true, the caller object
can update the record that is returned by the find method.
See the next example from the InventTable:

static InventTable find(ItemId itemId, boolean update = false)
{
InventTable inventTable;
;
inventTable.selectForUpdate(update);
if (itemId)
{
select firstonly inventTable
index hint ItemIdx
where inventTable.ItemId == itemId;
}
return inventTable;
}

exists :-
As with the find method, there should also exist an exists method.
It basically works the same as the find method, except that it just returns true if a
record with the unique index specified by the input parameter(s) is found.
In the next example from the InventTable you can see that it returns true if the
input parameter has a value AND the select statement returns a value.

static boolean exist(ItemId itemId)
{
return itemId && (select RecId from inventTable
index hint ItemIdx
where inventTable.ItemId == itemId
).RecId != 0;
}