阅读下列程序，写出程序运行结果。 public class Test_l {  public static void main (String args[ ]) {  Lefthand left; Righthand right; left=new Lefthand() ; right=new Righthand (); left.start (); right.start () ; } } class Lefthand extends Thread {  public void run() {  for ( int i=l; i<=5; i++) { System.out .print ("A"); try { sleep (500) ; } catch (InterruptedException e){} } } } class Righthand extends Thread {  public void run() {  for ( int i=l; i<=5; i++) {  System.out.print ("B"); try { sleep (300) ; } catch (InterruptedException e){} } } }