Functional vs. Imperative Programming

FunctionalPrime.java

public boolean isPrime(final int number) {  
    return number > 1 &&  
                IntStream.rangeClosed(2, (int) Math.sqrt(number))  
                        .noneMatch(index -> number % index == 0);
}

ImperativePrime.java

public boolean isPrime(final int number) {  
    for(int i = 2; i <= Math.sqrt(number); i++) {  
        if(number % i == 0) return false;  
    }  
    return number > 1;  
}