1 ps -eLf
首先，在Linux下，我们可以用ps -eLf命令看到java的线程号：
$ ps -eLf | grep java | grep -v grep
opt 10801 1 10801 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10806 0 23 Sep19 ? 00:00:02 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10807 0 23 Sep19 ? 00:00:25 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10808 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10809 0 23 Sep19 ? 00:00:27 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10810 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10811 0 23 Sep19 ? 00:00:51 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10812 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10813 0 23 Sep19 ? 00:00:16 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10814 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10815 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10816 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10817 0 23 Sep19 ? 00:00:20 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10818 0 23 Sep19 ? 00:00:06 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10819 0 23 Sep19 ? 00:00:02 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10820 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10821 0 23 Sep19 ? 00:04:35 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10822 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10825 0 23 Sep19 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10828 0 23 Sep19 ? 00:00:11 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10830 0 23 Sep19 ? 00:00:20 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 10831 0 23 Sep19 ? 00:00:20 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
opt 10801 1 19608 0 23 21:49 ? 00:00:00 java -XX:+UseG1GC -XX:+UseStringDeduplication -Xms32m -Xmx32m -server -jar gogo.jar
jstack
其次，我们可以使用jstack命令转储线程信息，也能得到java线程号：
"Reference Handler" #2 daemon prio=10 os_prio=0 cpu=30.65ms elapsed=339658.01s tid=0x00007fa6e0120000 nid=0x2a3e waiting on condition [0x00007fa6c435b000]
java.lang.Thread.State: RUNNABLE
at java.lang.ref.Reference.waitForReferencePendingList(java.base@11.0.3/Native Method)
at java.lang.ref.Reference.processPendingReferences(java.base@11.0.3/Reference.java:241)
at java.lang.ref.Reference$ReferenceHandler.run(java.base@11.0.3/Reference.java:213)
其中的nid=0x2a3e的十进制为10814：
$ printf "%d\n" 0x2a3e
10814
top -H -p
$ top -H -p 10801
top - 22:07:00 up 4 days, 26 min, 1 user, load average: 0.00, 0.00, 0.00
Threads: 23 total, 0 running, 23 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 1025532 total, 87060 free, 309220 used, 629252 buff/cache
KiB Swap: 266236 total, 243336 free, 22900 used. 565344 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
10801 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.00 java
10806 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:02.78 java
10807 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:26.07 GC Thread#0
10808 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.14 G1 Main Marker
10809 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:27.40 G1 Conc#0
10810 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.00 G1 Refine#0
10811 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:51.73 G1 Young RemSet
10812 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.02 StrDedup
10813 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:17.05 VM Thread
10814 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.02 Reference Handl
10815 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.02 Finalizer
10816 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.00 Signal Dispatch
10817 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:20.07 C2 CompilerThre
10818 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:06.41 C1 CompilerThre
10819 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:02.51 Sweeper thread
10820 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.00 Service Thread
10821 opt 20 0 2185948 187316 11692 S 0.0 18.3 4:36.19 VM Periodic Tas
10822 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.37 Common-Cleaner
10825 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.00 AsyncAppender-W
10828 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:11.31 nioEventLoopGro
10830 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:20.83 nioEventLoopGro
10831 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:20.76 nioEventLoopGro
19608 opt 20 0 2185948 187316 11692 S 0.0 18.3 0:00.00 Attach Listener
参考
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