java如何检查哪个线程(10个线程中的哪一个)被称为Singleton构造函数?
我试图找出(出于好奇)到底是哪个线程调用了单例构造函数。我完全理解测试程序每次执行的线程都是不同的,只是想实际检查相同的线程。我试过了
dumpStack()
printStackTrace()
getStackTrace()
but the does not give any hint of other class (!phew)
然后尝试在最后一行暂停线程,方法是放置一个wait(),以便使用jvisualvm检查线程转储,令人惊讶的是,我想要的信息也丢失了
有人能告诉我如何解决这个问题吗
Singleton类,从每个线程(10)的run()方法调用其getInstance()方法。但是对于其中一个线程调用,实际的构造函数将运行
package creational;
public class SingleTonBillPaugh
{
private SingleTonBillPaugh instance;
public static SingleTonBillPaugh getInstance()
{
return SingleTonHelper.instance;
}
private SingleTonBillPaugh()
{
System.out.println("instance is going to be created");
}
private static class SingleTonHelper
{
private static final SingleTonBillPaugh instance = new SingleTonBillPaugh();
}
}
用于单例和线程创建的测试类。注:obj。有意添加wait()以保持线程处于暂停模式,从而使它们能够在jvisualvm中进行检查
package creational;
import java.util.concurrent.TimeUnit;
public class SingleTonBillPaughTest
{
public static void main(String[] args)
{
Thread[] t = new SingleTonThread[10];
for (int i = 0; i < 10; i++)
{
t[i] = new SingleTonThread();
}
for (int i = 0; i < 10; i++)
{
t[i].start();
}
}
}
class SingleTonThread extends Thread
{
private Object obj = new Object();
public void run()
{
String threadName = Thread.currentThread().getName();
System.out.println(threadName);
try
{
TimeUnit.SECONDS.sleep(10);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
System.out.println(threadName + " " + SingleTonBillPaugh.getInstance());
// Thread.currentThread().dumpStack();
// new Throwable().printStackTrace();
// new Throwable().getStackTrace();
synchronized (obj)
{
try
{
obj.wait();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
}
}
来自jvisualvm的示例输出
2015-01-06 14:22:39
Full thread dump Java HotSpot(TM) 64-Bit Server VM (23.7-b01 mixed mode):
"DestroyJavaVM" prio=6 tid=0x00000000012ed800 nid=0x373c waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"Thread-9" prio=6 tid=0x000000000bc22800 nid=0x13b4 in Object.wait() [0x000000000dfaf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db3190> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db3190> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-8" prio=6 tid=0x000000000bc21800 nid=0x1b54 in Object.wait() [0x000000000deaf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db3028> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db3028> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-7" prio=6 tid=0x000000000bc1e000 nid=0x1128 in Object.wait() [0x000000000ddaf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db2ec0> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db2ec0> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-6" prio=6 tid=0x000000000bc19800 nid=0x2f7c in Object.wait() [0x000000000dcaf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db2d58> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db2d58> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-5" prio=6 tid=0x000000000bc18800 nid=0x3f30 in Object.wait() [0x000000000dbaf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db2bf0> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db2bf0> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-4" prio=6 tid=0x000000000bc18000 nid=0x31c8 in Object.wait() [0x000000000daaf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db2a88> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db2a88> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-3" prio=6 tid=0x000000000bc16800 nid=0x41c4 in Object.wait() [0x000000000d9af000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db2920> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db2920> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-2" prio=6 tid=0x000000000bc10000 nid=0x261c in Object.wait() [0x000000000d8af000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db27b8> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db27b8> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-1" prio=6 tid=0x000000000bc0f000 nid=0x30dc in Object.wait() [0x000000000d7af000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db2650> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db2650> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Thread-0" prio=6 tid=0x000000000bc0e000 nid=0x41b4 in Object.wait() [0x000000000d6af000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5db24e8> (a java.lang.Object)
at java.lang.Object.wait(Object.java:503)
at creational.SingleTonThread.run(SingleTonBillPaughTest.java:45)
- locked <0x00000007d5db24e8> (a java.lang.Object)
Locked ownable synchronizers:
- None
"Service Thread" daemon prio=6 tid=0x000000000bbe6000 nid=0x3554 runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"C2 CompilerThread1" daemon prio=10 tid=0x000000000bbe3800 nid=0x2084 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"C2 CompilerThread0" daemon prio=10 tid=0x000000000bbde000 nid=0x369c waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"Attach Listener" daemon prio=10 tid=0x000000000bbdd000 nid=0x4300 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"Signal Dispatcher" daemon prio=10 tid=0x000000000bbd9800 nid=0x3d88 runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE
Locked ownable synchronizers:
- None
"Finalizer" daemon prio=8 tid=0x000000000bb75000 nid=0x32cc in Object.wait() [0x000000000cfaf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5d65798> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(Unknown Source)
- locked <0x00000007d5d65798> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(Unknown Source)
at java.lang.ref.Finalizer$FinalizerThread.run(Unknown Source)
Locked ownable synchronizers:
- None
"Reference Handler" daemon prio=10 tid=0x000000000bb6c000 nid=0x29c8 in Object.wait() [0x000000000ceaf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d5d65320> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:503)
at java.lang.ref.Reference$ReferenceHandler.run(Unknown Source)
- locked <0x00000007d5d65320> (a java.lang.ref.Reference$Lock)
Locked ownable synchronizers:
- None
"VM Thread" prio=10 tid=0x000000000bb62800 nid=0x3cf0 runnable
"GC task thread#0 (ParallelGC)" prio=6 tid=0x0000000002b9d000 nid=0x3550 runnable
"GC task thread#1 (ParallelGC)" prio=6 tid=0x0000000002b9e800 nid=0x2e20 runnable
"GC task thread#2 (ParallelGC)" prio=6 tid=0x0000000002ba0800 nid=0x4254 runnable
"GC task thread#3 (ParallelGC)" prio=6 tid=0x0000000002ba2000 nid=0x3ddc runnable
"VM Periodic Task Thread" prio=10 tid=0x000000000bc03000 nid=0x2740 waiting on condition
JNI global references: 108
# 1 楼答案
只要说:
在构造函数中: