Some Hints for the Collections Exam


General: You can write code in just the main method, or you can write static
helper methods for duplicate code (or cut and paste duplicated code). It is 
better to finish each part of the problem and then immediately test/debug it,
than to write all the code and test/debug only at the end. 

Printing: When asked to print some collection that is NOT sorted, try to print
it using the implicit toString method for that class. It is an excellent idea
to print any collection this way first; if it prints correctly, then you should
proceed to writing the code for printing it sorted.

Sorting: Recall that for String values you can use Arrays.sort/Collection.sort
without supplying a Comparator (it uses the Comparable interface, which Strings
implement). This can be done in all the Collection Exam problems.

Constructors: Recall tht constructors for List/Set can take an argument
that is another List/Set, using an internal iterator to "add" each value from
the argument into the newly constructed collection. So, it is easy to create
a List/Set version of a Set/List: you don't have to write an iterator to solve
this problem.

Methods: For List/Set know about add, contains, addAll, remove, isEmpty, size,
and the Iterator (including remove). For Map know about put, get, keySet,
EntrySet, containsKey, containsValue, remove, values. Of course all these
(and more) can be viewed via the API.

Java 1.4 vs 1.5: If you use Java 1.4-style collections, you will get warnings
from Eclipse; you will also have to do your own casting. If you use Java
1.5-style collections, you must supply types in brackets; and if you do so
correctly, you will get no warnings and require no casting. Typically the size
of the solution is independent of this choice, although using the extended
"for" loop available in Java 1.5 can sometimes reduce the size of a solution
by a few lines.

Before the exam you should practice solving the pre-practice and practice
problems (both still available online) under timed conditions. I'd even
recommended solving one the morning of the exam, to get your brain thinking
about collection code.