diff --git a/src/MultiThreadDemo.java b/src/main/java/threaddemo/MultiThreadDemo.java
similarity index 70%
rename from src/MultiThreadDemo.java
rename to src/main/java/threaddemo/MultiThreadDemo.java
index c222e7b..6a41a6a 100644
--- a/src/MultiThreadDemo.java
+++ b/src/main/java/threaddemo/MultiThreadDemo.java
@@ -1,3 +1,5 @@
+package threaddemo;
+
 import java.lang.management.ThreadInfo;
 import java.lang.management.ThreadMXBean;
 
@@ -11,10 +13,7 @@ public class MultiThreadDemo {
         // 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("[" + threadInfo.getThreadId() + "] "
-                    + threadInfo.getThreadName()
-                    + "; Thread state: " + threadInfo.getThreadState()
-                    + " ; Is daemon: " + threadInfo.isDaemon()
+            System.out.println(STR."[\{threadInfo.getThreadId()}] \{threadInfo.getThreadName()}; Thread state: \{threadInfo.getThreadState()} ; Is daemon: \{threadInfo.isDaemon()}"
             );
         }
     }
diff --git a/src/ProcessDemo.java b/src/main/java/threaddemo/ProcessDemo.java
similarity index 98%
rename from src/ProcessDemo.java
rename to src/main/java/threaddemo/ProcessDemo.java
index 0739b54..8168a3b 100644
--- a/src/ProcessDemo.java
+++ b/src/main/java/threaddemo/ProcessDemo.java
@@ -1,3 +1,5 @@
+package threaddemo;
+
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
diff --git a/src/ThreadLocalDemo.java b/src/main/java/threaddemo/ThreadLocalDemo.java
similarity index 98%
rename from src/ThreadLocalDemo.java
rename to src/main/java/threaddemo/ThreadLocalDemo.java
index a8221dd..679b095 100644
--- a/src/ThreadLocalDemo.java
+++ b/src/main/java/threaddemo/ThreadLocalDemo.java
@@ -1,3 +1,5 @@
+package threaddemo;
+
 public class ThreadLocalDemo {
 
     public ThreadLocal<Integer> localVar = new ThreadLocal<>();
diff --git a/src/ThreadShareVariable.java b/src/main/java/threaddemo/ThreadShareVariable.java
similarity index 98%
rename from src/ThreadShareVariable.java
rename to src/main/java/threaddemo/ThreadShareVariable.java
index 8d39aef..4e074d5 100644
--- a/src/ThreadShareVariable.java
+++ b/src/main/java/threaddemo/ThreadShareVariable.java
@@ -1,4 +1,4 @@
-import java.util.stream.DoubleStream;
+package threaddemo;
 
 /**
  * 类ThreadShareVariable演示了线程间共享变量的使用和潜在风险
diff --git a/src/main/java/threaddemo/ThreadStateWithJoin.java b/src/main/java/threaddemo/ThreadStateWithJoin.java
new file mode 100644
index 0000000..8bdef61
--- /dev/null
+++ b/src/main/java/threaddemo/ThreadStateWithJoin.java
@@ -0,0 +1,35 @@
+package threaddemo;
+
+public class ThreadStateWithJoin {
+
+    public static void main(String[] args) throws InterruptedException {
+        Thread t1 = new Thread(() -> {
+            try {
+                Thread.sleep(1000);
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+        Thread t2 = new Thread(() -> {
+            try {
+                System.out.println("t2 start");
+                t1.join(100);
+
+                t1.join();
+                System.out.println("t2 end");
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+        t1.start();
+        t2.start();
+
+        Thread.sleep(20);
+        System.out.println(STR."t2 state: \{t2.getState()}");
+
+        Thread.sleep(100);
+        System.out.println(STR."t2 state: \{t2.getState()}");
+    }
+}
diff --git a/src/main/java/threaddemo/ThreadStateWithSync.java b/src/main/java/threaddemo/ThreadStateWithSync.java
new file mode 100644
index 0000000..29125d6
--- /dev/null
+++ b/src/main/java/threaddemo/ThreadStateWithSync.java
@@ -0,0 +1,19 @@
+package threaddemo;
+
+public class ThreadStateWithSync {
+
+    public static void main(String[] args) throws InterruptedException {
+        Thread t1 = new Thread(() -> {
+            synchronized (ThreadStateWithSync.class) {
+                System.out.println("t1 get lock ");
+            }
+        });
+
+        synchronized (ThreadStateWithSync.class) {
+            t1.start();
+            Thread.sleep(100L);
+
+            System.out.println(STR."t1 state: \{t1.getState()}");
+        }
+    }
+}
diff --git a/src/WeakReferenceExample.java b/src/main/java/threaddemo/WeakReferenceExample.java
similarity index 98%
rename from src/WeakReferenceExample.java
rename to src/main/java/threaddemo/WeakReferenceExample.java
index ca3421a..797903f 100644
--- a/src/WeakReferenceExample.java
+++ b/src/main/java/threaddemo/WeakReferenceExample.java
@@ -1,3 +1,5 @@
+package threaddemo;
+
 import java.lang.ref.WeakReference;
 
 public class WeakReferenceExample {