一、同步鎖(Lock):同步鎖是一個顯示鎖,需要通過 lock() 上鎖,通過 unlock() 釋放鎖
public class Test {
public static void main(String[] args) throws ExecutionException, InterruptedException {
Ticket ticket = new Ticket();
new Thread(ticket, "1號窗口").start();
new Thread(ticket, "2號窗口").start();
new Thread(ticket, "3號窗口").start();
}
}
class Ticket implements Runnable {
private int tickets = 100;
private Lock lock = new ReentrantLock();
@Override
public void run() {
// 加鎖
lock.lock();
try {
while (tickets > 0) {
Thread.sleep(100);
System.out.println(Thread.currentThread().getName() + " 完成售票,餘票爲:" + --tickets);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 釋放鎖
lock.unlock();
}
}
}
二、閉鎖(CountDownLatch):在要完成某些運算時,只有其它線程的運算全部運行完畢,當前運算才繼續下去。
例如:計算線程的執行時間
public class Test {
public static void main(String[] args) {
// 閉鎖計數器和其它線程數一樣
final CountDownLatch latch = new CountDownLatch(5);
LatchDemo ld = new LatchDemo(latch);
long start = System.currentTimeMillis();
for (int i = 0; i < 5; i++) {
// 其它運算線程開始執行
new Thread(ld).start();
}
try {
// 主線程等待其它線程全部執行完,才繼續下去,算出線程執行時間
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
long end = System.currentTimeMillis();
System.out.println("耗時:" + (end - start));
}
}
// 其它運算線程
class LatchDemo implements Runnable {
private CountDownLatch latch;
LatchDemo(CountDownLatch latch) {
this.latch = latch;
}
@Override
public void run() {
synchronized (this) {
try {
for (int i = 0; i < 50000; i++) {
if (i % 2 == 0) {
System.out.println(i);
}
}
} finally {
// 閉鎖每次減一
latch.countDown();
}
}
}
}