在下面的程序中，为什么在按下CTRL+aa键打印"hello,world"/kbd>不是吗？importjava.awt.event.*;importjavax.swing.*;publicclassKeyStrokeTest{publicstaticvoidmain(String[]args){JPanelpanel=newJPanel();/*addanewactionnamed"foo"tothepanel'sactionmap*/panel.getActionMap().put("foo",newAbstractAction(){publicvoidactionPerforme