Modify method in Data Class

[Mathew Sam]

DataInfo test = find((newData.getValues())[0]);
if ((test != null) &&
(test.getRecordNumber()!=newData.getRecordNumber()))
{
throw new DatabaseException("Attempt to create a "+
"duplicate key by modification");
}
Above is a code snippet from modify method of Data class.Do you think when a record is updated is this check required ?.Duplicate key check is only reqired when a new record is added. Is it not.

[HenkGijsbert]

Some naughty client might try to modify the key field of a record to the value of an already existing key. So it is necessary.

[Mathew Sam]

The find method is finding a record which has the same record number.Then again checking whether both the records are having same record number.I am not understanding the logic ? Am i missing some thing?

[HenkGijsbert]

The find method is NOT finding a method with the same record number, but with the same key value, wich is in the first field of a record:
newData.getValues()[0]. Please study the DataInfo class and the Data class to learn the difference between record number and key value.
Henk