1)现在有T1、T2、T3三个线程，你怎样保证T2在T1执行完后执行，T3在T2执行完后执行？

join（）方法：当某个程序执行流中调用其他线程的join方法，调用线程被阻塞，直到新join的线程执行完。

public class ThreadTest {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Thread thread1 = new Thread(){
@Override
public void run() {
// TODO Auto-generated method stub

try {
System.out.println("thread 1 running....");
sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
System.out.println("thread 1 stoped....");
}
super.run();
}
};
Thread thread2 = new Thread(){
@Override
public void run() {
// TODO Auto-generated method stub

try {
System.out.println("thread 2 running....");
sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
System.out.println("thread 2 stoped....");
}
super.run();
}
};
Thread thread3 = new Thread(){
@Override
public void run() {
// TODO Auto-generated method stub

try {
System.out.println("thread 3 running....");
sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
System.out.println("thread 3 stoped....");
}
super.run();
}
};
try {
thread1.start();
thread1.join();
thread2.start();
thread2.join();
thread3.start();
thread3.join();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}


}