本文主要對Java.util.concurrent中鎖的相關對比學習。

他們分別是：

① Object中wait和notify;

② Lock中lock.newCondition:condition.await()和condition.signal();

③LockSupport中靜態方法park和unpark;

一、先上結論：

① 對於Object中wait和notify：必須在鎖中使用，這裡指synchronized，並且wait方法要先於notify，否則wait方法會一直阻塞該該執行緒。

② Lock中lock.newCondition:condition.await()和condition.signal()：必須在鎖中使用，這裡指lock.lock()之後，並且await方法要先於singnal，否則await方法會一直阻塞該該執行緒。

③LockSupport優勢，優勢1：不需要再鎖中進行；優勢二：park方法可以不先於unpark方法。

二、測試程式碼

 1 public class LockAQS {
 2     private static Object objectLock = new Object();
 3     private static Lock lock = new ReentrantLock();
 4 
 5 
 6     public static void main(String[] args) {
 7 //        testWaitAndNotify();
 8 //        testLockAndUnLock();
 

 9         testParkAndUnPark();
10     }
11 
12     static void testParkAndUnPark(){
13         try {
14             TimeUnit.SECONDS.sleep(2);
15         } catch (InterruptedException e) {
16             e.printStackTrace();
17         }
18         Thread t1 = new Thread(() -> {
19             System.out.println(Thread.currentThread().getName() + "\t" + "come in");
 
20             LockSupport.park();
21             System.out.println(Thread.currentThread().getName() + "\t " + "被喚醒");
22         });
23         t1.start();
24         
25         new Thread(()->{
26             System.out.println(Thread.currentThread().getName() + "\t " + "通知其他");
27             LockSupport.unpark(t1);
28         }).start();
29 
30     }
31 
32     static void testLockAndUnLock() {
33         Condition condition = lock.newCondition();
34         new Thread(() -> {
35             try {
36                 TimeUnit.SECONDS.sleep(2);
37             } catch (InterruptedException e) {
38                 e.printStackTrace();
39             }
40             try {
41                 lock.lock();
42                 try {
43                     System.out.println(Thread.currentThread().getName() + "\t" + " come in");
44                     condition.await();
45                 } catch (InterruptedException e) {
46                     e.printStackTrace();
47                 }
48                 System.out.println(Thread.currentThread().getName() + "\t " + "被喚醒");
49             } finally {
50                 lock.unlock();
51             }
52         }, "LockA").start();
53 
54         new Thread(() -> {
55             try {
56                 lock.lock();
57                 System.out.println(Thread.currentThread().getName() + "\t " + "通知其他");
58                 condition.signal();
59             } finally {
60                 lock.unlock();
61             }
62         }, "LockB").start();
63     }
64 
65     static void testWaitAndNotify() {
66         new Thread(() -> {
67             try {
68                 Thread.sleep(2000);
69             } catch (InterruptedException e) {
70                 e.printStackTrace();
71             }
72             synchronized (objectLock) {
73                 System.out.println(Thread.currentThread().getName() + "\t" + "come in");
74                 try {
75                     objectLock.wait();
76                 } catch (InterruptedException e) {
77                     e.printStackTrace();
78                 }
79                 System.out.println(Thread.currentThread().getName() + "\t " + "被喚醒");
80             }
81         }, "A").start();
82 
83         new Thread(() -> {
84             synchronized (objectLock) {
85                 System.out.println(Thread.currentThread().getName() + "\t" + "通知其他");
86                 objectLock.notify();
87             }
88         }, "B").start();
89     }
90 }