Continous download plugin crashes as rememberErrorMessage is final

[mkoniecz]

What steps will reproduce the problem?

1. Enable ContinousDownload plugin
2. Start JOSM

What is the expected result?

Plugin works, as it was happening

What happens instead?

Plugin is unable to load

INFO: loading plugin 'continuosDownload' (version 1413902943)
ERROR: org.openstreetmap.josm.plugins.PluginException: An error occurred in plugin continuosDownload. Cause: java.lang.reflect.InvocationTargetException. Cause: java.lang.VerifyError: class org.openstreetmap.josm.plugins.continuosDownload.DownloadOsmTask2 overrides final method rememberErrorMessage.(Ljava/lang/String;)V
org.openstreetmap.josm.plugins.PluginException: An error occurred in plugin continuosDownload
	at org.openstreetmap.josm.plugins.PluginInformation.load(PluginInformation.java:336)
	at org.openstreetmap.josm.plugins.PluginHandler.loadPlugin(PluginHandler.java:698)
	at org.openstreetmap.josm.plugins.PluginHandler.loadPlugins(PluginHandler.java:758)
	at org.openstreetmap.josm.plugins.PluginHandler.loadLatePlugins(PluginHandler.java:797)
	at org.openstreetmap.josm.gui.MainApplication.main(MainApplication.java:463)
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
	at org.openstreetmap.josm.plugins.PluginInformation.load(PluginInformation.java:333)
	... 4 more
Caused by: java.lang.VerifyError: class org.openstreetmap.josm.plugins.continuosDownload.DownloadOsmTask2 overrides final method rememberErrorMessage.(Ljava/lang/String;)V
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at org.openstreetmap.josm.plugins.continuosDownload.DownloadPlugin.<init>(DownloadPlugin.java:54)

Please provide any additional information below. Attach a screenshot if possible.

Reported also as ​https://github.com/Gnonthgol/JOSM-continuos-download/issues/16 - I have no idea is it JOSM bug or a plugin bug.

Revision: 8926
Repository Root: http://josm.openstreetmap.de/svn
Relative URL: ^/trunk
Last Changed Author: Don-vip
Last Changed Date: 2015-10-22 02:01:00 +0200 (Thu, 22 Oct 2015)
Build-Date: 2015-10-22 01:32:36
URL: http://josm.openstreetmap.de/svn/trunk
Repository UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last Changed Rev: 8926

Identification: JOSM/1.5 (8926 en) Linux Ubuntu 14.04.3 LTS
Memory Usage: 272 MB / 889 MB (177 MB allocated, but free)
Java version: 1.8.0_60, Oracle Corporation, Java HotSpot(TM) Server VM

Plugins:
- OpeningHoursEditor (31603)
- RoadSigns (31603)
- continuosDownload
- measurement (31648)

Last errors/warnings:
- E: org.openstreetmap.josm.plugins.PluginException: An error occurred in plugin continuosDownload. Cause: java.lang.reflect.InvocationTargetException. Cause: java.lang.VerifyError: class org.openstreetmap.josm.plugins.continuosDownload.DownloadOsmTask2 overrides final method rememberErrorMessage.(Ljava/lang/String;)V

[Don-vip]

In 8927/josm:

fix #11998 - add two new protected boolean members to simplify customization of OSM download task for plugins + fix some javadoc/sonar issues