Showing a list of plugins to filter
Early Return

You can return early to reduce the nesting of your if statements:

if (plugins.isEmpty()) {
    plugin = null;
    return;
}


Also note that I changed plugins.size() &gt; 0 to !plugins.isEmpty(), I think it's more readable.

Plugins Field

Code like this:


plugins = pluginManager.getPlugins(); // assign field

plugins = filterPlugins(searchParam); // method expects plugins field to be assigned, 
                                      // but doesn't work on it but returns instead



Can be a bit confusing. I would change it to:

plugins = filterPlugins(pluginManager.getPlugins(), searchParam);


And then change filterPlugins to:

private List&lt;Plugin&gt; filterPlugins(final List&lt;Plugin&gt; plugins, final String searchParam )


plugin field

I would still like to see the declaration of plugin as well as the selectPlugin method. As mentioned in the comments, it looks a bit like it might be bad design.