Same example expressed functionally.

demo/03/src/main/java/pl/amu/edu/demo/primes/FunctionalPrimes.java

@@ -0,0 +1,30 @@
+package pl.amu.edu.demo.primes;
+
+import lombok.NoArgsConstructor;
+
+import java.util.function.IntPredicate;
+import java.util.stream.IntStream;
+
+@NoArgsConstructor
+public class FunctionalPrimes {
+
+    public static void main(String[] args) {
+        new FunctionalPrimes().printPrimes();
+    }
+
+    public void printPrimes() {
+        IntStream.range(0, 121)
+                .filter(this::isPrime)
+                .forEach(i -> System.out.printf("%d is prime\n", i));
+    }
+
+    private boolean isPrime(int number) {
+        if (number <= 0) {
+            return false;
+        }
+        IntPredicate isDivisible = (int divisor) -> number % divisor == 0;
+        return IntStream.rangeClosed(2, (int) Math.sqrt(number))
+                .noneMatch(isDivisible);
+    }
+
+}