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.
No, String is already implementing the Comparable interface, so you don't need anything. In fact, it has nothing to do with equals(). but with Comparable or Comparator. You either implement Comparable, or you provide your own Comparator and pass it as the third parameter of binarySearch.