Review fixes

Signed-off-by: Jorge Bescos Gascon <jorge.bescos.gascon@oracle.com>

impl/src/main/java/org/eclipse/parsson/JsonMergePatchImpl.java

@@ -16,6 +16,8 @@
 
 package org.eclipse.parsson;
 
+import java.util.Objects;
+
 import jakarta.json.JsonMergePatch;
 import jakarta.json.JsonObject;
 import jakarta.json.JsonObjectBuilder;
@@ -121,11 +123,16 @@ static JsonValue diff(JsonValue source, JsonValue target) {
      */
     @Override
     public boolean equals(Object obj) {
-        if (this == obj)
+        if (this == obj) {
             return true;
-        if (obj == null || obj.getClass() != JsonMergePatchImpl.class)
+        } else if (obj == null) {
+            return false;
+        } else if (getClass() != JsonMergePatchImpl.class) {
             return false;
-        return patch.equals(((JsonMergePatchImpl)obj).patch);
+        } else {
+            JsonMergePatchImpl other = (JsonMergePatchImpl) obj;
+            return Objects.equals(patch, other.patch);
+        }
     }
 
     /**
@@ -135,7 +142,7 @@ public boolean equals(Object obj) {
      */
     @Override
     public int hashCode() {
-        return patch.hashCode();
+        return Objects.hashCode(patch);
     }
 
     /**

impl/src/test/java/org/eclipse/parsson/tests/JsonMergePatchImplTest.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2022 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0, which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the
+ * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+ * version 2 with the GNU Classpath Exception, which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ */
+
+package org.eclipse.parsson.tests;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.eclipse.parsson.JsonMergePatchImpl;
+import org.junit.Test;
+
+import jakarta.json.Json;
+
+public class JsonMergePatchImplTest {
+
+    @Test
+    public void testEquals() {
+        JsonMergePatchImpl j1 = new JsonMergePatchImpl(Json.createValue("test"));
+        JsonMergePatchImpl j2 = new JsonMergePatchImpl(Json.createValue("test"));
+        JsonMergePatchImpl j3 = new JsonMergePatchImpl(j1.toJsonValue());
+        JsonMergePatchImpl j4 = new JsonMergePatchImpl(Json.createValue("test2"));
+        JsonMergePatchImpl j5 = new JsonMergePatchImpl(null);
+
+        assertTrue(j1.equals(j1));
+
+        assertTrue(j1.equals(j2));
+        assertTrue(j2.equals(j1));
+
+        assertTrue(j1.equals(j3));
+        assertTrue(j3.equals(j1));
+
+        assertTrue(j2.equals(j3));
+        assertTrue(j3.equals(j2));
+
+        assertFalse(j1.equals(j4));
+        assertFalse(j1.equals(j5));
+        assertFalse(j1.equals(null));
+    }
+}