Is there a difference between null and NULL?

[carsten (Carsten Wuthenow)]

After switching to openhab 2.3 and re-engineering all my KNX items and things I had some strange behaviors with some rules. Deep diving I found ItemStateEvents that change the state of an item from null to NULL. Working with a lot of hash maps in my rules I have a lot of If statements that filter items states that contains a null (!== null). As I’m not an expert in Java I was wondering if there is a difference between null and NULL and in which use-case I need to check whether a “null” or a “NULL” state of an item.

Hope someone can bring some light into this

Carsten

[sihui]

After openhabe 2.3 update, homematic binding don't update item status

Not quite right. null !== NULL NULL is an Object of type State and it is a special State Items can have to indicated the Item is uninitialized. As an Object, NULL does have a .equals method so == should be used. null is a primitive speical work in the programming langauge to indicate no value. As a primitive, null does not have a .equals method so one should use the identity operator === instead of the equivalency operator ==. So === and !== should only be used with null and never used with N…

[SOLVED] Error in rules (Cannot reference the field 'NULL' before it is defined)

NULL != null NULL is a special State that an Item can have to indicate it is uninitialized. null is a programming construct that means no value. The two are distinct be and not interchangeable.

[carsten (Carsten Wuthenow)]

Great! thx for clarification. Could not really use the search function on this or I was too stupid to run the search case sensitive

[sihui]

@carsten

Could not really use the search function on this

Just include @rlkoshak in your searches and you will find almost any solution

[carsten (Carsten Wuthenow)]

Yes I know

Root cause for the strange behavior found: I used find+replace function to replace != null to !== null in my rules. I think that operation was not done case sensitive and it was also replaced for the states. Maybe a good learning for others who switch to 2.3