ObjectService: ensure getName() returns non-null

Author: ctrueden

src/main/java/org/scijava/object/DefaultObjectService.java

@@ -110,14 +110,16 @@ public void removeObject(final Object obj) {
 
 	@Override
 	public String getName(Object obj) {
-		String name = objectIndex.getName(obj);
-		if (name != null) {
-			return name;
-		}
+		if (obj == null) throw new NullPointerException();
+		final String name = objectIndex.getName(obj);
+		if (name != null) return name;
 		if (obj instanceof Named) {
-			return ((Named) obj).getName();
+			final String n = ((Named) obj).getName();
+			if (n != null) return n;
 		}
-		return obj.toString();
+		final String s = obj.toString();
+		if (s != null) return s;
+		return obj.getClass().getName() + "@" + Integer.toHexString(obj.hashCode());
 	}
 
 	// -- Service methods --

src/main/java/org/scijava/object/ObjectService.java

@@ -57,11 +57,13 @@ default EventService eventService() {
 
 	/**
 	 * Gets the name belonging to a given object.
-	 * 
+	 * <p>
 	 * If no explicit name was provided at registration time, the name will be
-	 * derived from {@link Named#getName()} if the object implements {@link Named},
-	 * or from the {@link Object#toString()} otherwise
-	 **/
+	 * derived from {@link Named#getName()} if the object implements
+	 * {@link Named}, or from the {@link Object#toString()} otherwise. It is
+	 * guaranteed that this method will not return {@code null}.
+	 * </p>
+	 */
 	String getName(Object obj);
 
 	/** Registers an object with the object service. */