Java 11 Cookbook

How to do it...

1. Let's implement the APIs in the com.packt.math.MathUtil class, starting with the isPrime(Integer number) API:

        public static Boolean isPrime(Integer number){
          if ( number == 1 ) { return false; }
          return IntStream.range(2,num).noneMatch(i -> num % i == 0 );
        }

2. Implement the sumOfFirstNPrimes(Integer count) API:

        public static Integer sumOfFirstNPrimes(Integer count){
          return IntStream.iterate(1,i -> i+1)
                          .filter(j -> isPrime(j))
                          .limit(count).sum();
        }

3. Let's write a function to check whether the number is even:

        public static Boolean isEven(Integer number){
          return number % 2 == 0;
        }

4. The negation of isEven tells us whether the number is odd. We ...