@Override
    public int hashCode() {
        int hash = 5;
        hash = 71 * hash + (super.hashCode());
        hash = 71 * hash + (this.matExts != null ? this.matExts.hashCode() : 0);
        return hash;
    }
<code>OgreMaterialKey</code> allows specifying material extensions, which map
from Ogre3D base materials to jME3 materials
jme3-plugins/src/ogre/java/com/jme3/scene/plugins/ogre/matext/OgreMaterialKey.java