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public class Widget {
    private int noOfComponents;
    public Widget(int noOfComponents) {
        this.noOfComponents = noOfComponents;
    }
    public int getNoOfComponents() {
        return noOfComponents;
    }
    public void setNoOfComponents(int noOfComponents) {
        this.noOfComponents = noOfComponents;
    }

	// Also overrides hashcode() (code is omitted) ...

    public boolean equals(Object o) {
        if (o == null || !(o instanceof Widget)) {
            return false;
        }
		// check for negative components
        if (noOfComponents < 0) {
            return false;
        }
        Widget widget = (Widget) o;
        return this.noOfComponents == ((Widget) o).getNoOfComponents();
    }
}

public class Navigator extends Widget {
    public Navigator(int noOfComponents) {
        super(noOfComponents);
    }
    @Override
    public boolean equals(Object o) {
        if (o == null) {
            return false;
        }
        return true;
    }
}

public class LayoutManager {
    private Set<Widget> layouts = new HashSet<Widget>();
    public void addWidget(Widget widget) {
        if (!layouts.contains(widget)) {
            layouts.add(widget);
        }
    }
    public int getLayoutSize() {
        return layouts.size();
    }
}