Make Objects.requireNonNull() throw IllegalArgumentException

and not NullPointerException. Altough this differs from
java.util.Objects behavior, throwing an IllegalArgumentException
appears more sensible and makes it easier to catch it in Smack's
parsing function.

smack-core/src/main/java/org/jivesoftware/smack/util/Objects.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2015-2018 Florian Schmaus
+ * Copyright 2015-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,9 +20,26 @@ import java.util.Collection;
 
 public class Objects {
 
-    public static <T> T requireNonNull(T obj, String message) {
+    /**
+     * Checks that the specified object reference is not <code>null</code> and throws a customized
+     * {@link IllegalArgumentException} if it is.
+     * <p>
+     * Note that unlike <code>java.util.Objects</code>, this method throws an {@link IllegalArgumentException} instead
+     * of an {@link NullPointerException}.
+     * </p>
+     *
+     * @param <T> the type of the reference.
+     * @param obj the object reference to check for nullity.
+     * @param message detail message to be used in the event that a {@link IllegalArgumentException} is thrown.
+     * @return <code>obj</code> if not null.
+     * @throws IllegalArgumentException in case <code>obj</code> is <code>null</code>.
+     */
+    public static <T> T requireNonNull(T obj, String message) throws IllegalArgumentException {
         if (obj == null) {
-            throw new NullPointerException(message);
+            if (message == null) {
+                message = "Can not provide null argument";
+            }
+            throw new IllegalArgumentException(message);
         }
         return obj;
     }

smack-core/src/test/java/org/jivesoftware/smack/packet/PresenceTest.java

@@ -20,10 +20,11 @@ import static org.jivesoftware.smack.test.util.XmlUnitUtils.assertXmlSimilar;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.io.IOException;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 import org.xml.sax.SAXException;
 
 public class PresenceTest {
@@ -59,9 +60,11 @@ public class PresenceTest {
         assertXmlSimilar(control, presenceTypeSet.toXML(StreamOpen.CLIENT_NAMESPACE).toString());
     }
 
-    @Test(expected = NullPointerException.class)
+    @Test
     public void setNullPresenceTypeTest() {
-        getNewPresence().setType(null);
+        assertThrows(IllegalArgumentException.class, () ->
+        getNewPresence().setType(null)
+        );
     }
 
     @Test
@@ -112,9 +115,11 @@ public class PresenceTest {
         assertXmlSimilar(control, presence.toXML(StreamOpen.CLIENT_NAMESPACE).toString());
     }
 
-    @Test(expected = IllegalArgumentException.class)
+    @Test
     public void setIllegalPriorityTest() {
-        getNewPresence().setPriority(Integer.MIN_VALUE);
+        assertThrows(IllegalArgumentException.class, () ->
+        getNewPresence().setPriority(Integer.MIN_VALUE)
+        );
     }
 
     @Test

smack-experimental/src/test/java/org/jivesoftware/smackx/reference/ReferenceTest.java

@@ -98,7 +98,7 @@ public class ReferenceTest extends SmackTestSuite {
 
     @Test
     public void typeArgumentNullTest() throws URISyntaxException {
-        assertThrows(NullPointerException.class, () ->
+        assertThrows(IllegalArgumentException.class, () ->
         new ReferenceElement(1, 2, null, null, new URI("xmpp:test@test.test")));
     }
 

smack-extensions/src/test/java/org/jivesoftware/smackx/jingle/JingleContentTest.java

@@ -32,7 +32,7 @@ import org.junit.Test;
  */
 public class JingleContentTest extends SmackTestSuite {
 
-    @Test(expected = NullPointerException.class)
+    @Test(expected = IllegalArgumentException.class)
     public void emptyBuilderThrowsTest() {
         JingleContent.Builder builder = JingleContent.getBuilder();
         builder.build();

smack-extensions/src/test/java/org/jivesoftware/smackx/jingle/JingleTest.java

@@ -41,7 +41,7 @@ public class JingleTest extends SmackTestSuite {
         builder.build();
     }
 
-    @Test(expected = NullPointerException.class)
+    @Test(expected = IllegalArgumentException.class)
     public void onlySessionIdBuilderTest() {
         String sessionId = "testSessionId";