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?

使用join()方法

public class TestJoin
{
public static void main(String[] args)
{
Thread t1 = new Thread(new T1(), "线程1");
Thread t2 = new Thread(new T2(), "线程2");
Thread t3 = new Thread(new T3(), "线程3");

try
{
//t1先启动
t1.start();
t1.join();
//t2
t2.start();
t2.join();
//t3
t3.start();
t3.join();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
}

class T1 implements Runnable{

@Override
public void run()
{
for (int i = 0; i < 5; i++)
{
System.out.println(Thread.currentThread().getName()+": "+i);
try
{
Thread.sleep(100);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
}
}
class T2 implements Runnable{

@Override
public void run()
{
for (int j = 5; j < 10; j++)
{
System.out.println(Thread.currentThread().getName()+": "+j);
try
{
Thread.sleep(100);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
}
}
class T3 implements Runnable{
@Override
public void run()
{
for (int i = 10; i < 15; i++)
{
System.out.println(Thread.currentThread().getName()+": "+i);
try
{
Thread.sleep(100);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
}
}还有一种方式，在t3开始前join t2，在t2开始前join t1
public class TestJoin2
{
public static void main(String[] args)
{
final Thread t1 = new Thread(new Runnable() {

@Override
public void run() {
System.out.println("t1");
}
});
final Thread t2 = new Thread(new Runnable() {

@Override
public void run() {
try {
//引用t1线程，等待t1线程执行完
t1.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("t2");
}
});
Thread t3 = new Thread(new Runnable() {

@Override
public void run() {
try {
//引用t2线程，等待t2线程执行完
t2.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("t3");
}
});
t3.start();
t2.start();
t1.start();
}
}

转自：http://www.cnblogs.com/yzlpersonal/p/5231681.html

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