NEW: Just starting up, i.e., in process of being initialized.
NEW_TRANS: Corresponding transition state (not used, included for completness).
IN_NATIVE: Running in native code.
IN_NATIVE_TRANS: Corresponding transition state.
IN_VM: Running in VM.
IN_VM_TRANS: Corresponding transition state.
IN_JAVA: Running in Java or in stub code.
IN_JAVA_TRANS: Corresponding transition state (not used, included for completness).
BLOCKED: Blocked in vm.
BLOCKED_TRANS: Corresponding transition state.
IN_NATIVE 指的是在執行native方法，netty會有大量該狀態的線程
諾曼對 in_native的解釋：https://github.com/netty/netty/issues/8000