diff --git a/core-java/src/test/java/org/baeldung/java/collections/CollectionsToAndFromStringUnitTest.java b/core-java/src/test/java/org/baeldung/java/collections/CollectionsToAndFromStringUnitTest.java
new file mode 100644
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--- /dev/null
+++ b/core-java/src/test/java/org/baeldung/java/collections/CollectionsToAndFromStringUnitTest.java
@@ -0,0 +1,110 @@
+package org.baeldung.java.collections;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+
+public class CollectionsToAndFromStringUnitTest {
+	@Test
+	public void whenConvertArrayToString_thenConverted() {
+		String[] colors = new String[] { "Red", "Blue", "Green", "Yellow" };
+		String result = Arrays.stream(colors).collect(Collectors.joining(", "));
+
+		assertEquals(result, "Red, Blue, Green, Yellow");
+	}
+
+	@Test
+	public void whenConvertListToString_thenConverted() {
+		List<String> directions = Arrays.asList("Left", "Right", "Top", "Bottom");
+		String result = directions.stream().collect(Collectors.joining(", "));
+
+		assertEquals(result, "Left, Right, Top, Bottom");
+	}
+
+	@Test
+	public void whenConvertMapToString_thenConverted() {
+		Map<Integer, String> users = new HashMap<>();
+		users.put(1, "John Doe");
+		users.put(2, "Paul Smith");
+		users.put(3, "Susan Anderson");
+
+		String result = users.entrySet().stream()
+				.map(entry -> entry.getKey() + " = " + entry.getValue())
+				.collect(Collectors.joining(", "));
+
+		assertEquals(result, "1 = John Doe, 2 = Paul Smith, 3 = Susan Anderson");
+	}
+
+	@Test
+	public void whenConvertNestedListToString_thenConverted() {
+		List<List<String>> nested = new ArrayList<>();
+		nested.add(Arrays.asList("Left", "Right", "Top", "Bottom"));
+		nested.add(Arrays.asList("Red", "Blue", "Green", "Yellow"));
+
+		String result = nested.stream()
+				.map(nextList -> nextList.stream()
+						.collect(Collectors.joining("-")))
+				.collect(Collectors.joining("; "));
+
+		assertEquals(result, "Left-Right-Top-Bottom; Red-Blue-Green-Yellow");
+	}
+
+	@Test
+	public void whenConvertListToStringAndSkipNull_thenConverted() {
+		List<String> fruits = Arrays.asList("Apple", "Orange", null, "Grape");
+		String result = fruits.stream()
+				.filter(next -> next != null)
+				.collect(Collectors.joining(", "));
+
+		assertEquals(result, "Apple, Orange, Grape");
+	}
+
+	@Test
+	public void whenConvertStringToArray_thenConverted() {
+		String colors = "Red, Blue, Green, Yellow";
+		String[] result = colors.split(", ");
+
+		assertArrayEquals(result, new String[] { "Red", "Blue", "Green", "Yellow" });
+	}
+
+	@Test
+	public void whenConvertStringToList_thenConverted() {
+		String colors = "Left, Right, Top, Bottom";
+		List<String> result = Arrays.asList(colors.split(", "));
+
+		assertTrue(result.equals(Arrays.asList("Left", "Right", "Top", "Bottom")));
+	}
+
+	@Test
+	public void whenConvertStringToMap_thenConverted() {
+		String users = "1 = John Doe, 2 = Paul Smith, 3 = Susan Anderson";
+
+		Map<Integer, String> result = Arrays.stream(users.split(", "))
+				.map(next -> next.split(" = "))
+				.collect(Collectors.toMap(entry -> Integer.parseInt(entry[0]), entry -> entry[1]));
+
+		assertEquals(result.get(1), "John Doe");
+		assertEquals(result.get(2), "Paul Smith");
+		assertEquals(result.get(3), "Susan Anderson");
+	}
+
+	@Test
+	public void whenConvertListToStringMultipleSeparators_thenConverted() {
+		String fruits = "Apple. , Orange, Grape. Lemon";
+
+		List<String> result = Arrays.stream(fruits.split("[,|.]"))
+				.map(String::trim).filter(next -> !next.isEmpty())
+				.collect(Collectors.toList());
+
+		assertTrue(result.equals(Arrays.asList("Apple", "Orange", "Grape", "Lemon")));
+	}
+}