网站必须备案吗,推广广告赚佣金,wordpress上传权限设置,老师让做网站怎么做1、定义
即 Guarded Suspension#xff0c;用在一个线程等待另一个线程的执行结果
要点 有一个结果需要从一个线程传递到另一个线程#xff0c;让他们关联同一个 GuardedObject 如果有结果不断从一个线程到另一个线程那么可以使用消息队列 JDK 中#xff0c;join 的实现…1、定义
即 Guarded Suspension用在一个线程等待另一个线程的执行结果
要点 有一个结果需要从一个线程传递到另一个线程让他们关联同一个 GuardedObject 如果有结果不断从一个线程到另一个线程那么可以使用消息队列 JDK 中join 的实现、Future 的实现采用的就是此模式 因为要等待另一方的结果因此归类到同步模式 2、实现
class GuardedObject {
// 结果private Object response;private final Object lock new Object();
// 获取结果public Object get() {synchronized (lock) {// 条件不满足则等待while (response null) {try {lock.wait();} catch (InterruptedException e) {e.printStackTrace();}}return response;}}
// 产生结果public void complete(Object response) {synchronized (lock) {// 条件满足通知等待线程this.response response;lock.notifyAll();}}
}
3、应用
一个线程等待另一个线程的执行结果
public static void main(String[] args) {GuardedObject guardedObject new GuardedObject();new Thread(() - {try {// 子线程执行下载ListString response download(); // 模拟下载操作log.debug(download complete...);guardedObject.complete(response);} catch (IOException e) {e.printStackTrace();}}).start();
log.debug(waiting...);// 主线程阻塞等待Object response guardedObject.get();log.debug(get response: [{}] lines, ((ListString) response).size());
}
执行结果
08:42:18.568 [main] c.TestGuardedObject - waiting...
08:42:23.312 [Thread-0] c.TestGuardedObject - download complete...
08:42:23.312 [main] c.TestGuardedObject - get response: [3] lines
4、带超时版 GuardedObject
如果要控制超时时间呢
class GuardedObjectV2 {
private Object response;private final Object lock new Object();
public Object get(long millis) {synchronized (lock) {// 1) 记录最初时间long begin System.currentTimeMillis();// 2) 已经经历的时间long timePassed 0;while (response null) {// 4) 假设 millis 是 1000结果在 400 时唤醒了那么还有 600 要等long waitTime millis - timePassed;log.debug(waitTime: {}, waitTime);if (waitTime 0) {log.debug(break...);break;}try {lock.wait(waitTime); // 注意这里并不是 mills防止虚假唤醒} catch (InterruptedException e) {e.printStackTrace();}// 3) 如果提前被唤醒这时已经经历的时间假设为 400timePassed System.currentTimeMillis() - begin;log.debug(timePassed: {}, object is null {}, timePassed, response null);}return response;}}
public void complete(Object response) {synchronized (lock) {// 条件满足通知等待线程this.response response;log.debug(notify...);lock.notifyAll();}}
}
测试没有超时
public static void main(String[] args) {GuardedObjectV2 v2 new GuardedObjectV2();new Thread(() - {sleep(1); // 睡眠1秒v2.complete(null);sleep(1);v2.complete(Arrays.asList(a, b, c));}).start();
Object response v2.get(2500);if (response ! null) {log.debug(get response: [{}] lines, ((ListString) response).size());} else {log.debug(cant get response);}
}
输出
08:49:39.917 [main] c.GuardedObjectV2 - waitTime: 2500
08:49:40.917 [Thread-0] c.GuardedObjectV2 - notify...
08:49:40.917 [main] c.GuardedObjectV2 - timePassed: 1003, object is null true
08:49:40.917 [main] c.GuardedObjectV2 - waitTime: 1497
08:49:41.918 [Thread-0] c.GuardedObjectV2 - notify...
08:49:41.918 [main] c.GuardedObjectV2 - timePassed: 2004, object is null false
08:49:41.918 [main] c.TestGuardedObjectV2 - get response: [3] lines
测试超时
// 等待时间不足
ListString lines v2.get(1500);
输出
08:47:54.963 [main] c.GuardedObjectV2 - waitTime: 1500
08:47:55.963 [Thread-0] c.GuardedObjectV2 - notify...
08:47:55.963 [main] c.GuardedObjectV2 - timePassed: 1002, object is null true
08:47:55.963 [main] c.GuardedObjectV2 - waitTime: 498
08:47:56.461 [main] c.GuardedObjectV2 - timePassed: 1500, object is null true
08:47:56.461 [main] c.GuardedObjectV2 - waitTime: 0
08:47:56.461 [main] c.GuardedObjectV2 - break...
08:47:56.461 [main] c.TestGuardedObjectV2 - cant get response
08:47:56.963 [Thread-0] c.GuardedObjectV2 - notify...
5、多任务版 GuardedObject
图中 Futures 就好比居民楼一层的信箱每个信箱有房间编号左侧的 t0t2t4 就好比等待邮件的居民右侧的 t1t3t5 就好比邮递员
如果需要在多个类之间使用 GuardedObject 对象作为参数传递不是很方便因此设计一个用来解耦的中间类这样不仅能够解耦【结果等待者】和【结果生产者】还能够同时支持多个任务的管理 新增 id 用来标识 Guarded Object
class GuardedObject {
// 标识 Guarded Objectprivate int id;
public GuardedObject(int id) {this.id id;}
public int getId() {return id;}
// 结果private Object response;
// 获取结果// timeout 表示要等待多久 2000public Object get(long timeout) {synchronized (this) {// 开始时间 15:00:00long begin System.currentTimeMillis();// 经历的时间long passedTime 0;while (response null) {// 这一轮循环应该等待的时间long waitTime timeout - passedTime;// 经历的时间超过了最大等待时间时退出循环if (timeout - passedTime 0) {break;}try {this.wait(waitTime); // 虚假唤醒 15:00:01} catch (InterruptedException e) {e.printStackTrace();}// 求得经历时间passedTime System.currentTimeMillis() - begin; // 15:00:02 1s}return response;}}
// 产生结果public void complete(Object response) {synchronized (this) {// 给结果成员变量赋值this.response response;this.notifyAll();}}
}
中间解耦类
class Mailboxes {private static MapInteger, GuardedObject boxes new Hashtable();
private static int id 1;// 产生唯一 idprivate static synchronized int generateId() {return id;}
public static GuardedObject getGuardedObject(int id) {return boxes.remove(id); // 注意这里的remove防止堆溢出}
public static GuardedObject createGuardedObject() {GuardedObject go new GuardedObject(generateId());boxes.put(go.getId(), go);return go;}
public static SetInteger getIds() {return boxes.keySet();}
}
业务相关类
class People extends Thread{Overridepublic void run() {// 收信GuardedObject guardedObject Mailboxes.createGuardedObject();log.debug(开始收信 id:{}, guardedObject.getId());Object mail guardedObject.get(5000);log.debug(收到信 id:{}, 内容:{}, guardedObject.getId(), mail);}
}
class Postman extends Thread {private int id;private String mail;
public Postman(int id, String mail) {this.id id;this.mail mail;}
Overridepublic void run() {GuardedObject guardedObject Mailboxes.getGuardedObject(id);log.debug(送信 id:{}, 内容:{}, id, mail);guardedObject.complete(mail);}
}
测试
public static void main(String[] args) throws InterruptedException {for (int i 0; i 3; i) {new People().start();}Sleeper.sleep(1);// 睡眠1秒for (Integer id : Mailboxes.getIds()) {new Postman(id, 内容 id).start();}
}
某次运行结果
10:35:05.689 c.People [Thread-1] - 开始收信 id:3
10:35:05.689 c.People [Thread-2] - 开始收信 id:1
10:35:05.689 c.People [Thread-0] - 开始收信 id:2
10:35:06.688 c.Postman [Thread-4] - 送信 id:2, 内容:内容2
10:35:06.688 c.Postman [Thread-5] - 送信 id:1, 内容:内容1
10:35:06.688 c.People [Thread-0] - 收到信 id:2, 内容:内容2
10:35:06.688 c.People [Thread-2] - 收到信 id:1, 内容:内容1
10:35:06.688 c.Postman [Thread-3] - 送信 id:3, 内容:内容3
10:35:06.689 c.People [Thread-1] - 收到信 id:3, 内容:内容3
