获取主线程启动的线程列表的代码片段:

import java.util.Set;

public class ThreadSet {
    public static void main(String args[]) throws Exception{
        Thread.currentThread().setName("ThreadSet");
        for ( int i=0; i< 3; i++){
            Thread t = new Thread(new MyThread());
            t.setName("MyThread:"+i);
            t.start();
        }
        Set<Thread> 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();
        }
    }
}

输出:

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

如果您需要包括系统线程在内的所有线程，这些线程还没有被您的程序启动，请删除以下条件。

if ( t.getThreadGroup() == Thread.currentThread().getThreadGroup())

现在输出:

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

    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<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<ng; i++) {
            listThreads(groups[i], indent + "  ");
        }
    }

是的，看一下如何获取线程列表。那页上有很多例子。

这是通过编程来实现的。如果你只是想在Linux上得到一个列表，至少你可以使用这个命令:

kill -3 processid

虚拟机将做一个线程转储到标准输出。

你可以尝试这样做:

Thread.getAllStackTraces().keySet().forEach((t) -> System.out.println(t.getName() + "\nIs Daemon " + t.isDaemon() + "\nIs Alive " + t.isAlive()));

如果你需要，你可以得到更多的线程特性。

您可以使用返回所有活动线程id的getAllThreadIds。当此方法返回时，返回数组中包含的某些线程可能已经终止。

ManagementFactory.getThreadMXBean().getAllThreadIds()

获取一个可迭代集:

Set<Thread> threadSet = Thread.getAllStackTraces().keySet();

性能:0毫秒，12个线程(Azul JVM 16.0.1, Windows 10, Ryzen 5600X)。