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wait()方法源于Object类，当线程调用wait的时候，意思就是说线程会放弃对象锁，进入等待此对象的等待锁定池。
下面看看用jstack怎么定位wait方法。
首先写一段简单的调用wait的代码：
import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;class WaitTask implements Runnable{ @Override public void run(){ synchronized (this) { try{ wait(); }catch (InterruptedException e) { e.printStackTrace(); } } }}public class ThreadWait{ public static void main(String[] args) { WaitTask waitTask = new WaitTask(); ExecutorService executorService = Executors.newFixedThreadPool(1); executorService.execute(waitTask); }} 通过jps找到对应进程的id，然后用jstack跟踪一下：
$ jstack -l 303942016-11-07 16:36:47Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.101-b13 mixed mode):"Attach Listener" #12 daemon prio=9 os_prio=0 tid=0x00007fd2e4001000 nid=0x76ff runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None"DestroyJavaVM" #11 prio=5 os_prio=0 tid=0x00007fd32400a800 nid=0x76bb waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None"pool-1-thread-1" #10 prio=5 os_prio=0 tid=0x00007fd324145000 nid=0x76d1 in Object.wait() [0x00007fd30a4da000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00000000ec2174e8> (a WaitTask) at java.lang.Object.wait(Object.java:502) at WaitTask.run(ThreadWait.java:13) - locked <0x00000000ec2174e8> (a WaitTask) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - <0x00000000ec2b3758> (a java.util.concurrent.ThreadPoolExecutor$Worker)"Monitor Ctrl-Break" #9 daemon prio=5 os_prio=0 tid=0x00007fd324142000 nid=0x76c9 runnable [0x00007fd30aaf3000] java.lang.Thread.State: RUNNABLE at java.net.PlainSocketImpl.socketAccept(Native Method) at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409) at java.net.ServerSocket.implAccept(ServerSocket.java:545) at java.net.ServerSocket.accept(ServerSocket.java:513) at com.intellij.rt.execution.application.AppMain$1.run(AppMain.java:90) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - None"Service Thread" #8 daemon prio=9 os_prio=0 tid=0x00007fd3240c8800 nid=0x76c7 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None"C1 CompilerThread2" #7 daemon prio=9 os_prio=0 tid=0x00007fd3240bd000 nid=0x76c6 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None"C2 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007fd3240bb800 nid=0x76c5 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007fd3240b8800 nid=0x76c4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007fd3240b7000 nid=0x76c3 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007fd324084000 nid=0x76c2 in Object.wait() [0x00007fd30bdfc000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00000000ec188ee0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143) - locked <0x00000000ec188ee0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209) Locked ownable synchronizers: - None"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007fd32407f800 nid=0x76c1 in Object.wait() [0x00007fd30befd000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00000000ec186b50> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference.tryHandlePending(Reference.java:191) - locked <0x00000000ec186b50> (a java.lang.ref.Reference$Lock) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153) Locked ownable synchronizers: - None"VM Thread" os_prio=0 tid=0x00007fd324078000 nid=0x76c0 runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007fd32401f800 nid=0x76bc runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007fd324021000 nid=0x76bd runnable "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007fd324023000 nid=0x76be runnable "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007fd324024800 nid=0x76bf runnable "VM Periodic Task Thread" os_prio=0 tid=0x00007fd3240cb000 nid=0x76c8 waiting on condition JNI global references: 15
这一段表示jstack已经检测到了wait()正在执行。
"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007fd324084000 nid=0x76c2 in Object.wait() [0x00007fd30bdfc000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00000000ec188ee0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143) - locked <0x00000000ec188ee0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209) Locked ownable synchronizers: - None"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007fd32407f800 nid=0x76c1 in Object.wait() [0x00007fd30befd000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00000000ec186b50> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference.tryHandlePending(Reference.java:191) - locked <0x00000000ec186b50> (a java.lang.ref.Reference$Lock) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153) Locked ownable synchronizers: - None
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