This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Your A class does not override the equals method, therefore it inherits it from the Object class, which means that a1.equals(a2) is exactly the same as a1 == a2. i.e. it will only be true if a1 and a2 refer to the same object, which in this case they don't.
You need to override equals and return the result of comparing the two lists