Java多執行緒知識點總結——進階篇(八) 之 等待喚醒機制 Lock 鎖升級版
阿新 • • 發佈:2019-01-01
JDK1.5 中提供了多執行緒升級解決方案。
將同步 Synchronized 替換成現實 Lock 操作。
將Object中的 wait、notify、notifyAll,替換成了Condition 物件。該物件可以對 Lock 鎖進行獲取。該示例中,實現了本方只喚醒對方操作。
Lock: 替代了 Synchronized,關鍵API有:
lock ()
unlock()
newCondition()
Condition:替代了Object wait notify notifyAll,關鍵API有:
await()
signal()
signalAll()
將上一篇文章的程式碼通過 Lock 鎖進行升級,升級後的程式碼如下:
import java.util.concurrent.locks.*;
import java.util.concurrent.locks.Lock;
class ProducerConsumerDemo2 {
public static void main(String[] args) {
Resource r = new Resource();
Producer pro = new Producer(r);
Consumer con = new Consumer(r);
new Thread(pro).start();
new Thread(pro).start();
new Thread(con).start();
new Thread(con).start();
}
}
class Resource {
private String name;
private int count = 1;
private boolean flag = false;
private Lock lock = new ReentrantLock();
private Condition condition_pro = lock .newCondition();
private Condition condition_con = lock.newCondition();
public void set(String name) throws InterruptedException {
lock.lock();
try {
while (flag)
condition_pro.await();
this.name = name + "--" + count++;
System.out.println(Thread.currentThread().getName() + "...生產者.."
+ this.name);
flag = true;
condition_con.signal();//只喚醒 producer 的執行緒
} finally {
lock.unlock();//釋放鎖的動作一定要執行。
}
}
public void out() throws InterruptedException {
lock.lock();
try {
while (!flag)
condition_con.await();
System.out.println(Thread.currentThread().getName() + "...消費者........." + this.name);
flag = false;
condition_pro.signal();//只喚醒 Consumer 的執行緒
} finally {
lock.unlock();//釋放鎖的動作一定要執行。
}
}
}
class Producer implements Runnable {
private Resource res;
Producer(Resource res) {
this.res = res;
}
public void run() {
while (true) {
try {
res.set("+商品+");
} catch (InterruptedException e) {
}
}
}
}
class Consumer implements Runnable {
private Resource res;
Consumer(Resource res) {
this.res = res;
}
public void run() {
while (true) {
try {
res.out();
} catch (InterruptedException e) {
}
}
}
}