Create IdentityHashMapDemo.java

rahulXbarnwal · web-flow · commit 32bafcdbfced · 2026-03-15T03:26:44.000+05:30
diff --git a/src/learnCollections/IdentityHashMapDemo.java b/src/learnCollections/IdentityHashMapDemo.java
@@ -0,0 +1,34 @@
+package learnCollections;
+
+import java.util.HashMap;
+import java.util.IdentityHashMap;
+import java.util.Map;
+
+public class IdentityHashMapDemo {
+    public static void main(String[] args) {
+        String key1 = new String("key");
+        String key2 = new String("key");
+
+        Map<String, Integer> map = new HashMap<>();
+        // hashcode and equals
+        map.put(key1, 1); // hashcode1 --> index1
+        map.put(key2, 2); // hashcode1 --> index1 --> equals() --> replace value of key with 2
+        System.out.println(key1.equals(key2));
+        System.out.println(map);
+
+
+        // whether the class has overridden equals() and hashCode() or not, in IdentityHashMap, object class hashcode will be used which is based on memory address
+        // hence object hashcode will be considered for key1 and key2, which will be different
+        Map<String, Integer> identityMap = new IdentityHashMap<>();
+        System.out.println(System.identityHashCode(key1)); // 292938459
+        System.out.println(System.identityHashCode(key2)); // 917142466
+
+        System.out.println(key1.hashCode()); // 106079
+        System.out.println(key2.hashCode()); // 106079
+
+        // IdentityHashcode and ==
+        identityMap.put(key1, 1); // key1 --> index1
+        identityMap.put(key2, 2); // key2 --> index2 (different from key1)
+        System.out.println(identityMap); // {key=2, key=1}
+    }
+}
