Bael 7599 (#16022)

* BAEL-7490 read write file in separate thread

* Change the to try resources

* Update the code to sync with article

* BAEL-7599 find majority element

* Added additional check on unit test

* Update the index checking

* Update the return type to Integer

core-java-modules/core-java-arrays-operations-advanced-2/src/main/java/com/baeldung/majorityelement/FindMajorityElement.java

@@ -0,0 +1,95 @@
+package com.baeldung.majorityelement;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+public class FindMajorityElement {
+
+    public static Integer findMajorityElementUsingForLoop(int[] nums) {
+        int majorityThreshold = nums.length / 2;
+        Integer majorityElement = null;
+        for (int i = 0; i < nums.length; i++) {
+            int count = 0;
+            for (int j = 0; j < nums.length; j++) {
+                if (nums[i] == nums[j]) {
+                    count++;
+                }
+            }
+            if (count > majorityThreshold) {
+                return majorityElement = nums[i];
+            }
+        }
+        return majorityElement;
+    }
+
+    public static Integer findMajorityElementUsingSorting(int[] nums) {
+        Arrays.sort(nums);
+        int majorityThreshold = nums.length / 2;
+        int count = 0;
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] == nums[majorityThreshold]) {
+                count++;
+            }
+
+            if (count > majorityThreshold) {
+                return nums[majorityThreshold];
+            }
+        }
+        return null;
+    }
+
+    public static Integer findMajorityElementUsingHashMap(int[] nums) {
+        Map<Integer, Integer> frequencyMap = new HashMap<>();
+
+        for (int num : nums) {
+            frequencyMap.put(num, frequencyMap.getOrDefault(num, 0) + 1);
+        }
+
+        int majorityThreshold = nums.length / 2;
+        for (Map.Entry<Integer, Integer> entry : frequencyMap.entrySet()) {
+            if (entry.getValue() > majorityThreshold) {
+                return entry.getKey();
+            }
+        }
+        return null;
+    }
+
+    public static Integer findMajorityElementUsingMooreVoting(int[] nums) {
+        int majorityThreshold = nums.length / 2;
+        int candidate = nums[0];
+        int count = 1;
+
+        for (int i = 1; i < nums.length; i++) {
+            if (count == 0) {
+                candidate = nums[i];
+                count = 1;
+            } else if (candidate == nums[i]) {
+                count++;
+            } else {
+                count--;
+            }
+
+            System.out.println("Iteration " + i + ": [candidate - " + candidate + ", count - " + count + ", element - " + nums[i] + "]");
+        }
+
+        count = 0;
+        for (int num : nums) {
+            if (num == candidate) {
+                count++;
+            }
+        }
+        return count > majorityThreshold ? candidate : null;
+    }
+
+    public static void main(String[] args) {
+        int[] nums = {  2, 3, 2, 4, 2, 5, 2 };
+        Integer majorityElement = findMajorityElementUsingMooreVoting(nums);
+
+        if (majorityElement != null) {
+            System.out.println("Majority element with maximum occurrences: " + majorityElement);
+        } else {
+            System.out.println("No majority element found");
+        }
+    }
+}

core-java-modules/core-java-arrays-operations-advanced-2/src/test/java/com/baeldung/majorityelement/FindMajorityElementUnitTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.majorityelement;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class FindMajorityElementUnitTest {
+
+    @Test
+    void givenArrayWithMajorityElement_WhenUsingForLoop_ThenReturnFound() {
+        int[] nums = { 2, 3, 2, 4, 2, 5, 2 };
+        Integer result = FindMajorityElement.findMajorityElementUsingForLoop(nums);
+        assertEquals(2, result);
+    }
+
+    @Test
+    void givenArrayWithoutMajorityElement_WhenUsingForLoop_ThenNotFound() {
+        int[] nums = { 2, 2, 3, 3 };
+        Integer result = FindMajorityElement.findMajorityElementUsingForLoop(nums);
+        assertEquals(null, result);
+    }
+
+    @Test
+    public void givenArrayWithMajorityElement_WhenUsingSorting_ThenReturnFound() {
+        int[] nums = { 2, 3, 2, 4, 2, 5, 2 };
+        Integer result = FindMajorityElement.findMajorityElementUsingSorting(nums);
+        assertEquals(2, result);
+    }
+
+    @Test
+    public void givenArrayWithoutMajorityElement_WhenUsingSorting_ThenNotFound() {
+        int[] nums = { 2, 2, 3, 3 };
+        Integer result = FindMajorityElement.findMajorityElementUsingSorting(nums);
+        assertEquals(null, result);
+    }
+
+    @Test
+    void givenArrayWithMajorityElement_WhenUsingHashMap_ThenReturnFound() {
+        int[] nums = { 2, 3, 2, 4, 2, 5, 2 };
+        Integer result = FindMajorityElement.findMajorityElementUsingHashMap(nums);
+        assertEquals(2, result);
+    }
+
+    @Test
+    void givenArrayWithoutMajorityElement_WhenUsingHashMap_ThenNotFound() {
+        int[] nums = { 2, 2, 3, 3 };
+        Integer result = FindMajorityElement.findMajorityElementUsingHashMap(nums);
+        assertEquals(null, result);
+    }
+
+    @Test
+    void givenArrayWithMajorityElement_WhenUsingMooreVoting_ThenReturnFound() {
+        int[] nums = { 2, 3, 2, 4, 2, 5, 2 };
+        Integer result = FindMajorityElement.findMajorityElementUsingMooreVoting(nums);
+        assertEquals(2, result);
+    }
+
+    @Test
+    void givenArrayWithoutMajorityElement_WhenUsingMooreVoting_ThenNotFound() {
+        int[] nums = { 2, 2, 3, 3 };
+        Integer result = FindMajorityElement.findMajorityElementUsingMooreVoting(nums);
+        assertEquals(null, result);
+    }
+}