long tStart = System.currentTimeMillis(); 
System.out.println(Thread.currentThread().getName() + "开始");//打印开始标记 
for (int ii = 0; ii < threadNum; ii++) {//开threadNum个线程 
Runnable r = new Runnable(){ 
@Override 
public void run(){ 
System.out.println(Thread.currentThread().getName() + "开始"); 
//做一些事情... ... 
System.out.println(Thread.currentThread().getName() + "结束."); 
} 
} 
Thread t = new Thread(r); 
t.start(); 
} 
System.out.println(Thread.currentThread().getName() + "结束.");//打印结束标记 
long tEnd = System.currentTimeMillis(); 
System.out.println("总共用时:"+ (tEnd - tStart) + "millions"); 

public class ImportThread extends Thread { 
private static List<Thread> runningThreads = new ArrayList<Thread>(); 
public ImportThread() { 
} 
@Override 
public void run() { 
regist(this);//线程开始时注册 
System.out.println(Thread.currentThread().getName() + "开始...");//打印开始标记 
//做一些事情... ... 
unRegist(this);//线程结束时取消注册 
System.out.println(Thread.currentThread().getName() + "结束.");//打印结束标记 
} 
public void regist(Thread t){ 
  synchronized(runningThreads){  
    runningThreads.add(t); 
  } 
} 
public void unRegist(Thread t){ 
  synchronized(runningThreads){  
    runningThreads.remove(t); 
  } 
} 
public static boolean hasThreadRunning() { 
return (runningThreads.size() > 0);//通过判断runningThreads是否为空就能知道是否还有线程未执行完 
} 
} 

long tStart = System.currentTimeMillis(); 
System.out.println(Thread.currentThread().getName() + "开始");//打印开始标记 
for (int ii = 0; ii < threadNum; ii++) {//开threadNum个线程 
Thread t = new ImportThread(); 
t.start(); 
} 
while(true){//等待所有子线程执行完 
if(!ImportThread.hasThreadRunning()){ 
break; 
} 
Thread.sleep(500); 
} 
System.out.println(Thread.currentThread().getName() + "结束.");//打印结束标记 
long tEnd = System.currentTimeMillis(); 
System.out.println("总共用时:"+ (tEnd - tStart) + "millions"); 

  public class MyCountDown { 
private int count; 
public MyCountDown(int count){ 
this.count = count; 
} 
public synchronized void countDown(){ 
count--; 
} 
public synchronized boolean hasNext(){ 
return (count > 0); 
} 
public int getCount() { 
return count; 
} 
public void setCount(int count) { 
this.count = count; 
} 
} 

 public class ImportThread extends Thread { 
private MyCountDown c; 
public ImportThread(MyCountDown c) { 
this.c = c; 
} 
@Override 
public void run() { 
System.out.println(Thread.currentThread().getName() + "开始...");//打印开始标记 
//Do something 
c.countDown();//计时器减1 
System.out.println(Thread.currentThread().getName() + "结束. 还有" + c.getCount() + " 个线程");//打印结束标记 
} 
} 

System.out.println(Thread.currentThread().getName() + "开始");//打印开始标记 
MyCountDown c = new MyCountDown(threadNum);//初始化countDown 
for (int ii = 0; ii < threadNum; ii++) {//开threadNum个线程 
Thread t = new ImportThread(c); 
t.start(); 
} 
while(true){//等待所有子线程执行完 
if(!c.hasNext()) break; 
} 
System.out.println(Thread.currentThread().getName() + "结束.");//打印结束标记 

public class ImportThread extends Thread { 
private CountDownLatch threadsSignal; 
public ImportThread(CountDownLatch threadsSignal) { 
this.threadsSignal = threadsSignal; 
} 
@Override 
public void run() { 
System.out.println(Thread.currentThread().getName() + "开始..."); 
//Do somethings 
threadsSignal.countDown();//线程结束时计数器减1 
System.out.println(Thread.currentThread().getName() + "结束. 还有" + threadsSignal.getCount() + " 个线程"); 
} 
} 

CountDownLatch threadSignal = new CountDownLatch(threadNum);//初始化countDown 
for (int ii = 0; ii < threadNum; ii++) {//开threadNum个线程 
final Iterator<String> itt = it.get(ii); 
Thread t = new ImportThread(itt,sql,threadSignal); 
t.start(); 
} 
threadSignal.await();//等待所有子线程执行完 
System.out.println(Thread.currentThread().getName() + "结束.");//打印结束标记