题：要求用三个线程，按顺序打印1,2,3,4,5.... 71,72,73,74, 75.
线程1先打印1,2,3,4,5,
然后是线程2打印6,7,8,9,10,
然后是线程3打印11,12,13,14,15.
接着再由线程1打印16,17,18,19,20....
以此类推, 直到线程3打印到75。
分析：感觉出题人是要考察一下你是否能够很好的控制多线程，让他们有序的进行。
1、线程池：3个线程，需要使用并发库的线程池
2、锁（lcok）：在打印的时候，只允许一个线程进入，其他的线程等待
《—张孝祥老师的视频有专门讲解线程的额。—》
程序代码：
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class NumberPrinter {
private Lock lock = new ReentrantLock();
private Condition c1 = lock.newCondition();
private Condition c2 = lock.newCondition();
private Condition c3 = lock.newCondition();
private Map<Integer, Condition> condtionContext =
new HashMap<Integer, Condition>();
public NumberPrinter() {
condtionContext.put(Integer.valueOf(0), c1);
condtionContext.put(Integer.valueOf(1), c2);
condtionContext.put(Integer.valueOf(2), c3);
}
private int count = 0;
public void print(int id) {
lock.lock();
try {
while(count*5 < 75) {
int curID = calcID();
if (id == curID) {
for (int i = 1; i<=5; i++) {
System.out.print(count*5 +i+ ",");
}
System.out.println();
count++;
int nextID = calcID();
Condition nextCondition = condtionContext.get(
Integer.valueOf(nextID));
//通知下一线程
nextCondition.signal();
} else {
Condition condition = condtionContext.get(
Integer.valueOf(id));
condition.await();
}
}
//通知线程结束
for(Condition c : condtionContext.values()) {
c.signal();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
private int calcID() {
// TODO Auto-generated method stub
return count % 3;
}
/**
* @param args
*/
public static void main(String[] args) {
ExecutorService executor = Executors.newFixedThreadPool(3);
final CountDownLatch latch = new CountDownLatch(1);
final NumberPrinter printer = new NumberPrinter();
for (int i = 0; i < 3; i++) {
final int id = i;
executor.submit(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
try {
latch.await();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
printer.print(id);
}
});
}
System.out.println("三个任务开始顺序打印数字。。。。。。");
latch.countDown();
executor.shutdown();
}
}
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