wait()方法源於Object類，當執行緒呼叫wait的時候，意思就是說執行緒會放棄物件鎖，進入等待此物件的等待鎖定池。

下面看看用jstack怎麼定位wait方法。

首先寫一段簡單的呼叫wait的程式碼：

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);
    }
}

通過jps找到對應程序的id，然後用jstack跟蹤一下：

$ jstack -l 30394
2016-11-07 16:36:47
Full 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

這一段表示jstack已經檢測到了wait()正在執行。

"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