public Boolean getChecked() {
		switch( state ) {
			default:
			case UNSELECTED:	return false;
			case INDETERMINATE:	return null;
			case SELECTED:		return true;
		}
	}
Returns the state as {@link Boolean}.
Returns {@code null} if the state is {@link State#INDETERMINATE}.
<p>
Alternatively you can use {@link #getState()} to get state as {@link State} enum
or {@link #isIndeterminate()} to check only for indeterminate state.
flatlaf-extras/src/main/java/com/formdev/flatlaf/extras/components/FlatTriStateCheckBox.java