exception « collection « Java Collection Q&A

1. What are the pros and cons for different methods of checking a Collection for a null before adding to a Set?    stackoverflow.com

This is a follow up question to "Is there a basic Java Set implementation that does not permit nulls?". (thank you to all of those who helped with the answer) ...

2. UnsupportedOperationException on Collection    stackoverflow.com

While studying the Collection API, we find that some methods (add, remove,...) may throw a java.lang.UnsupportedOperationException if the current implementation of the Collection does not support those functionalities. Is there,actually, in the ...

3. Duplicate value exception in Set    stackoverflow.com

It is said that those structures which implement Set interface do not allow duplicate elements. I just want to know, what do they mean by duplicate? Duplicate in terms of the ...

4. java.lang.UnsupportedOperationException at java.util.AbstractList.remove(Unknown Source)    stackoverflow.com

I have tried below code

String s[]={"1","2","3","4"};  
Collection c=Arrays.asList(s);  
System.out.println(c.remove("1") +"  remove flag");  

System.out.println(" collcetion "+c);  

Exception in thread "main" java.lang.UnsupportedOperationException  
at java.util.AbstractList.remove(Unknown Source) ...

5. Collections and exceptions    coderanch.com

6. Exception in class with collection    forums.oracle.com

I don't need to check them in add, I need to check them in time when they are already in the collection. Elements in the collection have it's own thread and some how change their attributes. My question was: How to catch it in the class with collection? If in collection one of it's elements becomes out of criteria it must ...