This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
b and d Explanations : Line 3 will results in a compilation error because it is comparing collection of two different types. equals() in the ArrayList(implemented in AbstractList) compares all the collection objects one by one and if all matches it returns true else false.In this case there is no objects at all to compare with hence will return true.