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null values of collections

natarajan meghanathan
Ranch Hand

Joined: Feb 01, 2001
Posts: 130
Can anyone say how many null values are allowed in the following collections:
(1) ArrayList
(2) TreeMap
(3) LinkedList
(4) HashSet
(5) HashMap
I know hashtable does not allow any null values. The API does not clearly say this. It just says ArrayList, etc. allow values including null.

Sun Certified Programmer for Java 2 Platform
Val Dra
Ranch Hand

Joined: Jan 26, 2001
Posts: 439
(1) ArrayList
(2) TreeMap
(3) LinkedList
(4) HashSet
(5) HashMap
All of them allow null values. Try it. The only thing is in a set values must be unique. SO if you add another null the value will not be added or it will be removed and a new null value be added i don't remember.

Val SCJP <BR>going for SCJD
I agree. Here's the link:
subject: null values of collections
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