Design Patterns Java™ Workbook

Observer (Chapter 9)

SOLUTION 9.1

One solution is: public JSlider slider() { if (slider == null) { slider = new JSlider(); sliderMax = slider.getMaximum(); sliderMin = slider.getMinimum(); slider.addChangeListener(this); slider.setValue(slider.getMinimum()); } return slider; } public void stateChanged(ChangeEvent e) { double val = slider.getValue(); double tp = (val - sliderMin) / (sliderMax - sliderMin); burnPanel().setTPeak(tp); thrustPanel().setTPeak(tp); valueLabel().setText("" + tp); }

SOLUTION 9.2

One solution is shown in Figure B.9. To allow a label to register for slider events, the design in Figure B.9 creates a subclass of JLabel that implements ChangeListener. The new design lets the components that depend on the slider register their ...