solve #3019: Number of Changing Keys in java

Author: anishLearnsToCode

Diff for: README.md

@@ -884,7 +884,7 @@
 | 3005 | [Count Elements With Maximum Frequency](https://leetcode.com/problems/count-elements-with-maximum-frequency)                                                           |                                                                              [![Java](assets/java.png)](src/CountElementsWithMaximumFrequency.java)                                                                              |                                                                                                                                   |
 | 3010 | [Divide an Array Into Subarrays With Minimum Cost I](https://leetcode.com/problems/divide-an-array-into-subarrays-with-minimum-cost-i)                                 |                                                                         [![Java](assets/java.png)](src/DivideAnArrayIntoSubarraysWithMinimumCostI.java)                                                                          |                                                                                                                                   |
 | 3014 | [Minimum Number of Pushes to Type Word I](https://leetcode.com/problems/minimum-number-of-pushes-to-type-word-i)                                                       |                                                                              [![Java](assets/java.png)](src/MinimumNumberOfPushesToTypeWordI.java)                                                                               |                                                                                                                                   |
-| 3019 | [Number of Changing Keys](https://leetcode.com/problems/number-of-changing-keys)                                                                                       |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 3019 | [Number of Changing Keys](https://leetcode.com/problems/number-of-changing-keys)                                                                                       |                                                                                    [![Java](assets/java.png)](src/NumberOfChangingKeys.java)                                                                                     |                                                                                                                                   |
 | 3024 | [Type of Triangle](https://leetcode.com/problems/type-of-triangle)                                                                                                     |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3028 | [Ant on the Boundary](https://leetcode.com/problems/ant-on-the-boundary)                                                                                               |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3032 | 🔒 [Count Numbers With Unique Digits II](https://leetcode.com/problems/count-numbers-with-unique-digits-ii)                                                            |                                                                                                                                                                                                                                  |                                                                                                                                   |

Diff for: src/NumberOfChangingKeys.java

@@ -0,0 +1,19 @@
+// https://leetcode.com/problems/number-of-changing-keys
+// T: O(|s|)
+// S: O(1)
+
+public class NumberOfChangingKeys {
+    public int countKeyChanges(String s) {
+        int changes = 0;
+        for (int i = 1 ; i < s.length() ; i++) {
+            if (isDifferent(s.charAt(i - 1), s.charAt(i))) {
+                changes++;
+            }
+        }
+        return changes;
+    }
+
+    private static boolean isDifferent(char a, char b) {
+        return Character.toLowerCase(a) != Character.toLowerCase(b);
+    }
+}