Get a list of all threads currently running in Java

Question

Is there any way I can get a list of all running threads in the current JVM  including the threads not started by my class    Is it also possible to get the Thread and Class objects of all threads in the list   I want to be able to do this through code

User · Answer

To get a list of threads and their full states using the terminal, you can use the command below:

jstack -l <PID>

Which <PID> is the id of process running on your computer. To get the process id of your java process you can simply run the jps command.

Also, you can analyze your thread dump that produced by jstack in TDAs (Thread Dump Analyzer) such fastthread or spotify thread analyzer tool.

User · Answer

In the java console  hit Ctrl-Break  It will list all threads plus some information about the heap  This won t give you access to the objects of course  But it can be very helpful for debugging anyway

User · Answer

In Groovy you can call private methods     Get a snapshot of the list of all threads  Thread   threads   Thread getThreads     In Java  you can invoke that method using reflection provided that security manager allows it

User · Answer

Get a handle to the root ThreadGroup  like this   ThreadGroup rootGroup   Thread currentThread   getThreadGroup    ThreadGroup parentGroup  while   parentGroup   rootGroup getParent       null        rootGroup   parentGroup      Now  call the enumerate   function on the root group repeatedly  The second argument lets you get all threads  recursively   Thread   threads   new Thread rootGroup activeCount     while  rootGroup enumerate threads  true      threads length        threads   new Thread threads length   2       Note how we call enumerate   repeatedly until the array is large enough to contain all entries

User · Answer

To get an iterable set   Set lt Thread gt  threadSet   Thread getAllStackTraces   keySet

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public static void main String   args                 Walk up all the way to the root thread group         ThreadGroup rootGroup   Thread currentThread   getThreadGroup            ThreadGroup parent          while   parent   rootGroup getParent       null                rootGroup   parent                     listThreads rootGroup                      List all threads and recursively list all subgroup     public static void listThreads ThreadGroup group  String indent            System out println indent    Group     group getName                            group getClass                 int nt   group activeCount            Thread   threads   new Thread nt 2   10     nt is not accurate         nt   group enumerate threads  false               List every thread in the group         for  int i 0  i lt nt  i                  Thread t   threads i               System out println indent      Thread     t getName                                t getClass                                 Recursively list all subgroups         int ng   group activeGroupCount            ThreadGroup   groups   new ThreadGroup ng 2   10           ng   group enumerate groups  false            for  int i 0  i lt ng  i                  listThreads groups i   indent

User · Answer

Yes  take a look at getting a list of threads  Lots of examples on that page   That s to do it programmatically  If you just want a list on Linux at least you can just use this command   kill -3 processid   and the VM will do a thread dump to stdout

User · Answer

Code snippet to get list of threads started by main thread   import java util Set   public class ThreadSet       public static void main String args    throws Exception          Thread currentThread   setName  ThreadSet            for   int i 0  i lt  3  i                 Thread t   new Thread new MyThread                 t setName  MyThread   i               t start                      Set lt Thread gt  threadSet   Thread getAllStackTraces   keySet            for   Thread t   threadSet               if   t getThreadGroup      Thread currentThread   getThreadGroup                     System out println  Thread    t      state   t getState                                      class MyThread implements Runnable      public void run            try              Thread sleep 5000            catch Exception err               err printStackTrace                        output   Thread  Thread MyThread 2 5 main  state TIMED WAITING Thread  Thread MyThread 0 5 main  state TIMED WAITING Thread  Thread MyThread 1 5 main  state TIMED WAITING Thread  Thread ThreadSet 5 main  state RUNNABLE   If you need all threads including system threads  which have not been started by your program  remove below condition   if   t getThreadGroup      Thread currentThread   getThreadGroup      Now output   Thread  Thread MyThread 2 5 main  state TIMED WAITING Thread  Thread Reference Handler 10 system  state WAITING Thread  Thread MyThread 1 5 main  state TIMED WAITING Thread  Thread ThreadSet 5 main  state RUNNABLE Thread  Thread MyThread 0 5 main  state TIMED WAITING Thread  Thread Finalizer 8 system  state WAITING Thread  Thread Signal Dispatcher 9 system  state RUNNABLE Thread  Thread Attach Listener 5 system  state RUNNABLE

User · Answer

You can get a lot of information about threads from the ThreadMXBean   Call the static ManagementFactory getThreadMXBean   method to get a reference to the MBean

User · Answer

You can try something like this   Thread getAllStackTraces   keySet   forEach  t  - gt  System out println t getName       nIs Daemon     t isDaemon       nIs Alive     t isAlive        and you can obviously get more thread characteristic if you need

User · Answer

You can use getAllThreadIds that Returns all live thread IDs  Some threads included in the returned array may have been terminated when this method returns  ManagementFactory getThreadMXBean   getAllThreadIds

User · Answer

Have you taken a look at jconsole   This will list all threads running for a particular Java process   You can start jconsole from the JDK bin folder   You can also get a full stack trace for all threads by hitting Ctrl Break in Windows or by sending kill pid --QUIT in Linux

User · Answer

Apache Commons users can use ThreadUtils  The current implementation uses the walk the thread group approach previously outlined   for  Thread t   ThreadUtils getAllThreads            System out println t getName            t isDaemon

[java] Get a list of all threads currently running in Java

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