Add Anagram Checker in Java using HashMap

Author: Farheen Shabbir Shaikh

Strings/AnagramChecker.java

@@ -0,0 +1,51 @@
+/**
+ * AnagramChecker.java
+ * Checks whether two input strings are anagrams using a HashMap.
+ * Time Complexity: O(n), Space Complexity: O(n)
+ */
+
+import java.util.HashMap;
+
+public class AnagramChecker {
+
+    public static boolean areAnagrams(String str1, String str2) {
+        // Remove spaces and convert to lowercase
+        str1 = str1.replaceAll("\\s", "").toLowerCase();
+        str2 = str2.replaceAll("\\s", "").toLowerCase();
+
+        // Quick length check
+        if (str1.length() != str2.length()) {
+            return false;
+        }
+
+        // Count characters in first string
+        HashMap<Character, Integer> map = new HashMap<>();
+        for (char c : str1.toCharArray()) {
+            map.put(c, map.getOrDefault(c, 0) + 1);
+        }
+
+        // Subtract character counts using second string
+        for (char c : str2.toCharArray()) {
+            if (!map.containsKey(c)) {
+                return false;
+            }
+            map.put(c, map.get(c) - 1);
+            if (map.get(c) == 0) {
+                map.remove(c);
+            }
+        }
+
+        return map.isEmpty();
+    }
+
+    public static void main(String[] args) {
+        String s1 = "Listen";
+        String s2 = "Silent";
+
+        if (areAnagrams(s1, s2)) {
+            System.out.println("\"" + s1 + "\" and \"" + s2 + "\" are anagrams.");
+        } else {
+            System.out.println("\"" + s1 + "\" and \"" + s2 + "\" are NOT anagrams.");
+        }
+    }
+}