feat: add sieve of atkin algorithm (#6709)

* feat: add sieve of atkin algorithm

* fix: add full test coverage

* refactor: if condition braces

---------

Co-authored-by: a <alexanderklmn@gmail.com>

src/test/java/com/thealgorithms/maths/SieveOfAtkinTest.java

@@ -0,0 +1,47 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for the {@code SieveOfAtkin} class.
+ */
+class SieveOfAtkinTest {
+
+    @Test
+    void testGeneratePrimesLimit10() {
+        List<Integer> primes = SieveOfAtkin.generatePrimes(10);
+        // Assert the full expected list of primes
+        List<Integer> expected = List.of(2, 3, 5, 7);
+        assertEquals(expected, primes, "Primes up to 10 should match expected list");
+    }
+
+    @Test
+    void testGeneratePrimesLimit2() {
+        List<Integer> primes = SieveOfAtkin.generatePrimes(2);
+        List<Integer> expected = List.of(2);
+        assertEquals(expected, primes, "Primes up to 2 should include 2");
+    }
+
+    @Test
+    void testGeneratePrimesLimit1() {
+        List<Integer> primes = SieveOfAtkin.generatePrimes(1);
+        assertTrue(primes.isEmpty(), "Primes list should be empty when limit < 2");
+    }
+
+    @Test
+    void testGeneratePrimesLimit50() {
+        List<Integer> primes = SieveOfAtkin.generatePrimes(50);
+        List<Integer> expected = List.of(2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47);
+        assertEquals(expected, primes, "Primes up to 50 should match expected list");
+    }
+
+    @Test
+    void testGeneratePrimesNegativeLimit() {
+        List<Integer> primes = SieveOfAtkin.generatePrimes(-10);
+        assertTrue(primes.isEmpty(), "Primes list should be empty for negative limit");
+    }
+}