BAEL-4405 move probability examples to java-numbers-4

java-numbers-4/src/test/java/com/baeldung/probability/RandomInvokerUnitTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.probability;
+
+import org.assertj.core.data.Offset;
+import org.junit.Test;
+
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class RandomInvokerUnitTest {
+    @Test
+    public void givenProbability_whenInvoked_invokeWithProbability() {
+        RandomInvoker randomInvoker = new RandomInvoker();
+
+        int numberOfSamples = 1_000_000;
+        int probability = 10;
+        int howManyTimesInvoked = Stream.generate(() -> randomInvoker.withProbability(() -> 1, () -> 0, probability))
+                .limit(numberOfSamples)
+                .mapToInt(e -> e).sum();
+        int monteCarloProbability = (howManyTimesInvoked * 100) / numberOfSamples;
+
+        assertThat(monteCarloProbability).isCloseTo(probability, Offset.offset(1));
+    }
+}