move code to correct place

add Thread state related code

src/main/java/threaddemo/MultiThreadDemo.java

@@ -0,0 +1,20 @@
+package threaddemo;
+
+import java.lang.management.ThreadInfo;
+import java.lang.management.ThreadMXBean;
+
+public class MultiThreadDemo {
+
+    public static void main(String[] args) {
+        ThreadMXBean threadMXBean = java.lang.management.ManagementFactory.getThreadMXBean();
+
+        // 不需要获取同步的 monitor 和 synchronizer 信息，仅获取线程和线程堆栈信息
+        ThreadInfo[] threadInfos = threadMXBean.dumpAllThreads(false, false);
+        // 遍历线程信息，仅打印线程 ID 和线程名称信息
+        for (ThreadInfo threadInfo : threadInfos) {
+
+            System.out.println(STR."[\{threadInfo.getThreadId()}] \{threadInfo.getThreadName()}; Thread state: \{threadInfo.getThreadState()} ; Is daemon: \{threadInfo.isDaemon()}"
+            );
+        }
+    }
+}