How much to prepare for java..util portion

[Yan Lee]

Hi all:
I am preparing for SCJP1.4 from the K&B book. The collections portion seemed to be only briefly dealt with in the book. So I decided to go to the javadocs for the JDK and look up java.util. I understood the basics like the heirarchy of interfaces and the abstract implementations of the interfaces. The last layer is the implementation classes. There are so many of these, Map alone has 5 concrete implementations
(HashMap, IdentityHashMap, LinkedHashMap, TreeMap, WeakHashMap)
and I do not even understand why they are there and under what ciscumstances should one use them.
My questions are:
1. Why does java.util have so many concrete implementations and why would one choose one over the other?
2. To what depth should I cover java.util related topics for the exam.
3. Do you think that the collections framework has been designed well?
Thanks and regards.

[Madhav Lakkapragada]

1. Why does java.util have so many concrete implementations and why would one choose one over the other?
You positively should be able to identify where you would use what.
Atleast know the differences.
2. To what depth should I cover java.util related topics for the exam.
Know the differences, try some programming so you are
familiar with the methods. How to get next item?
How to check the size? Methods for such actions.....
3. Do you think that the collections framework has been designed well?
We can debate about this later, but first concentrate on the
differences and the learning aspects. Without knowing the differences,
we can't debate.