hackerrank java challenge

https://www.hackerrank.com/contests/codewhiz-java-march-2016/challenges

Not much algorithm but a nice exercise on Java features.

interface Comparable {
  int compareTo(E o);
}

try {
} catch (Exception e) {
  throw e;  // rethrow
}

lambda expression

https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html

num -> {
  for (int i = 2; i * i <= num; ++i) {
    if (num % i == 0) return false;
  }
  return true;
}