Java Runnable线程变量共享问题

int i=0;
synchronized (this){
for(;i<10000;i++){
sb.append(i+"\n");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
jtp.setText(sb.toString());
}

}

把synchronized 去掉看结果就知道了！