fix: add package and resolve checkstyle errors for TrappingRainwater.java

Author: Arzoo1701

src/main/java/com/thealgorithms/searches/TrappingRainwater.java

@@ -1,5 +1,4 @@
 package com.thealgorithms.searches;
-
 /**
  * Trapping Rainwater Problem
  * Given an array of non-negative integers representing the height of bars,
@@ -16,45 +15,34 @@
  */
 public class TrappingRainwater {
 
-    /**
-     * Calculates the total trapped rainwater.
-     *
-     * @param height an array representing elevation map
-     * @return total units of water trapped
-     */
-    public static int trap(int[] height) {
-        if (height == null || height.length == 0) {
-            return 0;
-        }
+    private TrappingRainwater() {
+        throw new UnsupportedOperationException("Utility class");
+    }
 
-        int left = 0, right = height.length - 1;
-        int leftMax = 0, rightMax = 0;
-        int trappedWater = 0;
+    public static int trap(int[] height) {
+        int left = 0;
+        int right = height.length - 1;
+        int leftMax = 0;
+        int rightMax = 0;
+        int result = 0;
 
         while (left < right) {
             if (height[left] < height[right]) {
                 if (height[left] >= leftMax) {
                     leftMax = height[left];
                 } else {
-                    trappedWater += leftMax - height[left];
+                    result += leftMax - height[left];
                 }
                 left++;
             } else {
                 if (height[right] >= rightMax) {
                     rightMax = height[right];
                 } else {
-                    trappedWater += rightMax - height[right];
+                    result += rightMax - height[right];
                 }
                 right--;
             }
         }
-
-        return trappedWater;
-    }
-
-    // Example test
-    public static void main(String[] args) {
-        int[] height = {4, 2, 0, 3, 2, 5};
-        System.out.println("Total trapped water: " + trap(height)); // Output: 9
+        return result;
     }
 }