题目描述 ：http://aclay.blog.163.com/blog/static/20846823520146161033859/
jvm提供了一个jstack的工具，可以把该jvm中运行的线程堆栈导出，具体见j.stack文件
比如
"DubboServerHandler-192.168.6.96:20880-thread-143" daemon prio=10 tid=0x00007f3d8006d000 nid=0x1807 waiting on condition [0x00007f3d67cfa000]java.lang.Thread.State: WAITING (parking)at sun.misc.Unsafe.park(Native Method)- parking to wait for <0x00007f3f7c16b630> (a java.util.concurrent.SynchronousQueue$TransferStack)at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)at java.util.concurrent.SynchronousQueue$TransferStack.awaitFulfill(SynchronousQueue.java:422)at java.util.concurrent.SynchronousQueue$TransferStack.transfer(SynchronousQueue.java:323)at java.util.concurrent.SynchronousQueue.take(SynchronousQueue.java:857)at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:947)