import javax.swing.*; import java.awt.*; import java.awt.event.MouseAdapter; import java.awt.event.MouseWheelEvent; import java.awt.event.MouseWheelListener;  public class jtaWheel {   JFrame jf;   JTextArea jta;   JScrollPane jsp;   MouseWheelListener sysWheel;   public jtaWheel(){     jf = new JFrame("滾動縮放");     jf.setBounds(500,500,600,400);     jta = new JTextArea();     jsp = new JScrollPane(jta,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,         JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);     sysWheel = jsp.getMouseWheelListeners()[0];//得到系統滾動事件     jsp.removeMouseWheelListener(sysWheel);//移除系統滾動，需要時添加     jsp.addMouseWheelListener(new event());     jf.add(jsp);     jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     jf.setVisible(true);   }   private class event extends MouseAdapter{     @Override     public void mouseWheelMoved(MouseWheelEvent e){       if(e.isControlDown()){//當ctrl鍵被按下，滾動為放大縮小         Font f = jta.getFont();         if(e.getWheelRotation()<0){//如果滾動條向前就放大文本           jta.setFont(new Font(f.getFamily(),f.getStyle(),f.getSize()+1));         }else if(e.getWheelRotation()>0){//滾動條向后就縮小文本           jta.setFont(new Font(f.getFamily(),f.getStyle(),f.getSize()-1));         }       }else{//當ctrl沒有被按下，則為系統滾動         jsp.addMouseWheelListener(sysWheel);         sysWheel.mouseWheelMoved(e);//觸發系統滾動事件。         jsp.removeMouseWheelListener(sysWheel);       }     }   }   public static void main(String[] args){     new jtaWheel();   } }