public class test{

    public static void print(){
        System.out.println("Running!");
    }

    public static void main(String[] args){
        while(true){
            try {
                Thread.sleep(10);
            } catch (Exception ex) {
                break;
            }
        }

    }
}

public class Demo10 extends JFrame implements KeyListener {

    public Demo10() {
        this.setTitle("键盘事件处理");
        this.setSize(300, 200);
        this.setLocationRelativeTo(this);// 窗口居中
        this.setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);// 窗口关闭动作处理
        this.addKeyListener(this);// 添加注册键盘事件监听器

    }

    @Override
    public void keyPressed(KeyEvent arg0) {// 敲击

        // TODO Auto-generated method stub

    }

    @Override
    public void keyReleased(KeyEvent arg0) {// 按下
        // TODO Auto-generated method stub
        if (arg0.getKeyCode() == 114) {// 114 F3对应的编码
            Demo10.print();
        }
    }

    @Override
    public void keyTyped(KeyEvent arg0) {// 释放
        // TODO Auto-generated method stub

    }

    public static void main(String[] args) {
        new Demo10();

    }

    public static void print() {
        System.out.println("Running!");
    }

}

------解决方案--------------------
不用窗口要全局监听 java实现费劲 要jni
定时的话简单 直接用timer类就可以了  
你百度一下吧