corrected typpo and addeed optimized code

Author: saurabh22111999

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

@@ -0,0 +1,53 @@
+package com.thealgorithms.searches;
+
+/**
+ * Trapping Rain Water
+ *
+ * Given n non-negative integers representing an elevation map where the width of
+ * each bar is 1, compute how much water it can trap after raining.
+ *
+ * Approach: Two-pointer optimized O(n) time and O(1) extra space.
+ */
+public final class TrappingRainWater {
+
+    private TrappingRainWater() {}
+
+    /**
+     * Compute trapped rain water amount for the given heights array.
+     *
+     * @param height array of non-negative integers
+     * @return total units of trapped water
+     * @throws IllegalArgumentException if height is null
+     */
+    public static int trap(final int[] height) {
+        if (height == null) {
+            throw new IllegalArgumentException("height array must not be null");
+        }
+
+        int left = 0;
+        int right = height.length - 1;
+        int leftMax = 0;
+        int rightMax = 0;
+        int trapped = 0;
+
+        while (left <= right) {
+            if (height[left] <= height[right]) {
+                if (height[left] >= leftMax) {
+                    leftMax = height[left];
+                } else {
+                    trapped += leftMax - height[left];
+                }
+                left++;
+            } else {
+                if (height[right] >= rightMax) {
+                    rightMax = height[right];
+                } else {
+                    trapped += rightMax - height[right];
+                }
+                right--;
+            }
+        }
+
+        return trapped;
+    }
+}

src/main/java/com/thealgorithms/strings/Upper.java

@@ -1,7 +1,6 @@
 package com.thealgorithms.strings;
 
 public final class Upper {
-
     private Upper() {
     }
 
@@ -16,7 +15,7 @@ public static void main(String[] args) {
     }
 
     /**
-     * Converts all the characters in this {@code String} to upper case.
+     * Converts all the characters in this {@code String} to upper case
      *
      * @param s the string to convert
      * @return the {@code String}, converted to uppercase.
@@ -29,29 +28,12 @@ public static String toUpperCase(String s) {
         if (s.isEmpty()) {
             return s;
         }
-
-        // Check if any lowercase letter exists before creating a new String
-        boolean hasLower = false;
-        for (int i = 0; i < s.length(); i++) {
-            if (Character.isLowerCase(s.charAt(i))) {
-                hasLower = true;
-                break;
-            }
-        }
-
-        // If no lowercase characters, return the same string
-        if (!hasLower) {
-            return s;
-        }
-
-        // Convert lowercase letters to uppercase
         char[] chars = s.toCharArray();
         for (int i = 0; i < chars.length; i++) {
             if (Character.isLowerCase(chars[i])) {
                 chars[i] = Character.toUpperCase(chars[i]);
             }
         }
-
         return new String(chars);
     }
 }

src/test/java/com/thealgorithms/searches/TrappingRainWaterTest.java

@@ -0,0 +1,38 @@
+package com.thealgorithms.searches;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+public class TrappingRainWaterTest {
+
+    @Test
+    public void testExample() {
+        int[] height = {4, 2, 0, 3, 2, 5};
+        assertEquals(9, TrappingRainWater.trap(height));
+    }
+
+    @Test
+    public void testEmpty() {
+        int[] height = {};
+        assertEquals(0, TrappingRainWater.trap(height));
+    }
+
+    @Test
+    public void testNoTrapping() {
+        int[] height = {0, 1, 2, 3, 4};
+        assertEquals(0, TrappingRainWater.trap(height));
+    }
+
+    @Test
+    public void testFlat() {
+        int[] height = {3, 3, 3, 3};
+        assertEquals(0, TrappingRainWater.trap(height));
+    }
+
+    @Test
+    public void testNull() {
+        assertThrows(IllegalArgumentException.class, () -> TrappingRainWater.trap(null));
+    }
+}