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.
One more remark : if you are planning to make more test with the Comparable interface, you should fulfill the compareTo requirements, or the collections supporing sorting (such as TreeSet) won't work properly. For example, the implementation of Sub.compareTo method is not correct, because a.compareTo(b) is not equal to - b.compareTo(a).
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