super(); if (model == null) throw new NullPointerException("No model."); this.model = model; this.name = name; model.addChangeListener(this);
this(model, null);
    ViewerAction(ImViewer model, String name)    {        super();        if (model == null) throw new NullPointerException("No model.");        this.model = model;        this.name = name;        model.addChangeListener(this);    }