Collection Utils test cases

Author: deepak-malik

src/com/deepak/data/structures/Utils/CollectionUtils.java

@@ -11,6 +11,7 @@
 
 /**
  * Utilities for collections i.e List
+ * Note : Finding min, max and rotate can also be added here
  * 
  * @author Deepak
  */
@@ -121,11 +122,19 @@ public static <T> List<T> shuffle(List<T> list) {
 	 */
 	public static <T> List<T> swap(List<T> list, int minIndex, int maxIndex) {
 		if (list != null && list.size() > 2 && maxIndex > minIndex) {
+			List<T> updatedList = new ArrayList<>();
 			T elementAtMinIndex = list.get(minIndex);
 			T elementAtMaxIndex = list.get(maxIndex);
-			list.add(minIndex, elementAtMaxIndex);
-			list.add(maxIndex, elementAtMinIndex);
-			return list;
+			for (int i = 0; i < list.size(); i++) {
+				if (i != minIndex && i != maxIndex) {
+					updatedList.add(i, list.get(i));
+				} else if (i == minIndex) {
+					updatedList.add(i, elementAtMaxIndex);
+				} else if (i == maxIndex) {
+					updatedList.add(i, elementAtMinIndex);
+				}
+			}
+			return updatedList;
 		}
 		return null;
 	}
@@ -139,31 +148,13 @@ public static <T> List<T> swap(List<T> list, int minIndex, int maxIndex) {
 	 */
 	public static <T> List<T> fill(List<T> list, T element) {
 		if (list != null && list.size() > 0) {
+			List<T> updatedList = new ArrayList<>();
 			for (int i = 0; i < list.size(); i++) {
-				list.add(i, element);
+				updatedList.add(element);
 			}
-			return list;
+			return updatedList;
 		}
 		return null;
 	}
 
-	/**
-	 * Method to find the minimum from the list
-	 * 
-	 * @param list
-	 * @param comparator
-	 * @return {@link T}
-	 */
-	public static <T> T min(List<T> list, Comparator<T> comparator) {
-		return null;
-	}
-
-	public static <T> T max(List<T> list, Comparator<T> comparator) {
-		return null;
-	}
-
-	public static <T> List<T> rotate(List<T> list, int n) {
-		return null;
-	}
-	
 }

test/com/deepak/data/structures/Utils/CollectionUtilsTest.java

@@ -1,5 +1,98 @@
+/**
+ * Data-Structures-In-Java
+ * CollectionUtilsTest.java
+ */
 package com.deepak.data.structures.Utils;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Test cases for collection utility methods
+ * 
+ * @author Deepak
+ */
 public class CollectionUtilsTest {
 
+	/**
+	 * Test case to check if a collection is empty
+	 */
+	@Test
+	public void testIsEmpty() {
+		List<String> list = new ArrayList<>();
+		Assert.assertTrue(CollectionUtils.isEmpty(list));
+		list.add("A");
+		Assert.assertFalse(CollectionUtils.isEmpty(list));
+	}
+
+	/**
+	 * Test cases for sort
+	 */
+	@Test
+	public void testSort() {
+		List<String> list = Arrays.asList("C", "A", "F", "B");
+		list = CollectionUtils.sort(list);
+		Assert.assertTrue(list.get(0) == "A");
+		Assert.assertTrue(list.get(1) == "B");
+		Assert.assertTrue(list.get(2) == "C");
+		Assert.assertTrue(list.get(3) == "F");
+	}
+
+	/**
+	 * Test case to reverse the collection
+	 */
+	@Test
+	public void testReverse() {
+		List<String> list = Arrays.asList("C", "A", "F", "B");
+		list = CollectionUtils.reverse(list);
+		Assert.assertTrue(list.get(0) == "B");
+		Assert.assertTrue(list.get(1) == "F");
+		Assert.assertTrue(list.get(2) == "A");
+		Assert.assertTrue(list.get(3) == "C");
+	}
+
+	/**
+	 * Test case to shuffle the collection
+	 */
+	@Test
+	public void testShuffle() {
+		List<String> list = Arrays.asList("C", "A", "F", "B");
+		List<String> updatedList = CollectionUtils.reverse(list);
+		Assert.assertTrue(list.size() == updatedList.size());
+	}
+
+	/**
+	 * Method to test swapping of elements when index is given
+	 */
+	@Test
+	public void testSwap() {
+		List<String> list = Arrays.asList("C", "A", "F", "B");
+		Assert.assertTrue(list.get(0) == "C");
+		Assert.assertTrue(list.get(1) == "A");
+		Assert.assertTrue(list.get(2) == "F");
+		Assert.assertTrue(list.get(3) == "B");
+		List<String> updatedList = CollectionUtils.swap(list, 1, 2);
+		Assert.assertTrue(updatedList.get(0) == "C");
+		Assert.assertTrue(updatedList.get(1) == "F");
+		Assert.assertTrue(updatedList.get(2) == "A");
+		Assert.assertTrue(updatedList.get(3) == "B");
+	}
+
+	/**
+	 * Test case to check fill functionality
+	 */
+	@Test
+	public void testFill() {
+		List<String> list = Arrays.asList("C", "A", "F", "B");
+		list = CollectionUtils.fill(list, "M");
+		Assert.assertTrue(list.get(0) == "M");
+		Assert.assertTrue(list.get(1) == "M");
+		Assert.assertTrue(list.get(2) == "M");
+		Assert.assertTrue(list.get(3) == "M");
+	}
+
 }