bar为一JScrollBar组件，阅读下面，请在程序中的画线处填入正确的语句使程序能够正确运行。 ... public WellAdjusted() { super('Well Adjusted'); setSize(350,100); bar.addAdjustmentListener(this); value.setHorizontalAlignment(SwingConstants.CENTER); value.setEditable(false); JPanel pane = new JPane(); pane.setLayout(new BorderLayout()); pane.add(value,'Center'): pane.add(bar,'South'); setContentPane(pane); } public void adjustmentValueChanged(AdjustmentEvent evt) { 【 】 if(source ==bar) { int newValue bar.getValue(); value.setText(''+newValue); } repaint(); }