在下列E类中【代码】输出结果是_____. import java.awt.*; import java.awt.event.*; public class E implements Runnable { StringBuffer buffer=new StringBuffer(); Thread t1,t2; E() { t1=new Thread(this); t2=new Thread(this); } public synchronized void addChar(char c) { if(Thread.currentThread()==t1) { while(buffer.length()==0) { try{ wait(); } catch(Exception e){} } buffer.append(c); } if(Thread.currentThread()==t2) { buffer.append(c); notifyAll(); } } public static void main(String s[]) { E hello=new E(); hello.t1.start(); hello.t2.start(); while(hello.t1.isAlive()||hello.t2.isAlive()){} System.out.println(hello.buffer); //【代码】 } public void run() { if(Thread.currentThread()==t1) addChar('A') ; if(Thread.currentThread()==t2) addChar('B') ; } }