线程转储文件中有什么呢？

包含每一个线程的状态及调用堆栈信息。

1.thread dump 

jstack pid 

可以输出堆栈信息到控制台，可用重定向命令写入到文件中。

2.分析

结果为普通文本，可以直接阅读。形如：

2016-11-04 23:53:16
Full thread dump OpenJDK 64-Bit Server VM (24.95-b01 mixed mode):

"JDWP Transport Listener: dt_socket" daemon prio=10 tid=0x00007f1b280af000 nid=0x10e4 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Attach Listener" daemon prio=10 tid=0x00007f1b20e59800 nid=0x5c2 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"ajp-nio-8009-exec-10" daemon prio=10 tid=0x00007f1b20e58000 nid=0x6fef waiting on condition [0x00007f1b0eae9000]
   java.lang.Thread.State: WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x00000000df72b840> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
	at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
	at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
	at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:103)
	at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:31)
	at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)

3.线程状态

大致有RUNNABLE,WAITING ,TIMED_WAITING,BLOCKED这四种状态。

看到很多TIMED_WAITING不要担心，我们若用了java.util.concurrent.ThreadPoolExecutor 这个线程池，那么空闲的线程显示的就是TIMED_WAITING状态。因为它内部是BlockingQueue来盛放任务，若为空，get()的时候自然会阻塞。