diff --git a/src/main/java/hxy/bytecode/lock/ReentrantLockTest.java b/src/main/java/hxy/bytecode/lock/ReentrantLockTest.java
index b2de45f96fa51ef51c652140e0359a1935d38264..5a37573e821afda6c22c289cc19e8795de37a9dd 100644
--- a/src/main/java/hxy/bytecode/lock/ReentrantLockTest.java
+++ b/src/main/java/hxy/bytecode/lock/ReentrantLockTest.java
@@ -1,5 +1,6 @@
 package hxy.bytecode.lock;
 
+import java.util.ArrayList;
 import java.util.concurrent.locks.ReentrantLock;
 
 /**
@@ -19,12 +20,20 @@ public class ReentrantLockTest extends Thread {
 
     @Override
     public void run() {
+        ArrayList<Integer> a = new ArrayList();
 //        10000000
         for (int j = 0; j < 100000; j++) {
+            a.add(j);
             lock.lock();
             try {
-                System.out.println(this.getName() + " " + i);
-                i++;
+//                这就是可重入，对于同一把锁是可以获取两次的。 https://www.jianshu.com/p/155260c8af6c 有啥意义
+                lock.lock();
+                try {
+                    System.out.println(this.getName() + " " + i);
+                    i++;
+                } finally {
+                    lock.unlock();
+                }
             } finally {
                 lock.unlock();
             }
diff --git a/src/main/java/hxy/bytecode/thread/multi/AddRunnable.java b/src/main/java/hxy/bytecode/thread/multi/AddRunnable.java
new file mode 100644
index 0000000000000000000000000000000000000000..0bca2f510e99aa22ffd475e26325899f6453006f
--- /dev/null
+++ b/src/main/java/hxy/bytecode/thread/multi/AddRunnable.java
@@ -0,0 +1,27 @@
+package hxy.bytecode.thread.multi;
+
+import java.util.ArrayList;
+
+/**
+ * @author eric
+ * @program bytecode
+ * @description \
+ * @date 2021/5/15
+ */
+public class AddRunnable implements Runnable {
+    @Override
+    public void run() {
+        ArrayList<Integer> objects = new ArrayList<>();
+        for (int i = 0; i < 100000000; i++) {
+            objects.add(i);
+        }
+        System.out.println(objects.size());
+    }
+
+    public static void main(String[] args) {
+
+        new Thread(new AddRunnable(), "线程1").start();
+        new Thread(new AddRunnable(), "线程2").start();
+
+    }
+}
diff --git a/src/main/java/hxy/bytecode/thread/multi/AddRunnable2.java b/src/main/java/hxy/bytecode/thread/multi/AddRunnable2.java
new file mode 100644
index 0000000000000000000000000000000000000000..d1074fae84613351370d578232935f856d8ca46e
--- /dev/null
+++ b/src/main/java/hxy/bytecode/thread/multi/AddRunnable2.java
@@ -0,0 +1,28 @@
+package hxy.bytecode.thread.multi;
+
+import java.util.ArrayList;
+
+/**
+ * @author eric
+ * @program bytecode
+ * @description \
+ * @date 2021/5/15
+ */
+public class AddRunnable2 implements Runnable {
+
+    ArrayList<Integer> objects = new ArrayList<>();
+
+    @Override
+    public void run() {
+        for (int i = 0; i < 1000; i++) {
+            objects.add(i);
+        }
+    }
+
+    public static void main(String[] args) {
+
+        new Thread(new AddRunnable2(), "线程1").start();
+        new Thread(new AddRunnable2(), "线程2").start();
+
+    }
+}
diff --git a/src/main/java/hxy/bytecode/thread/multi/AddRunnable3.java b/src/main/java/hxy/bytecode/thread/multi/AddRunnable3.java
new file mode 100644
index 0000000000000000000000000000000000000000..4d028f16727dc69723de7607b8a803f3e8c8e5e9
--- /dev/null
+++ b/src/main/java/hxy/bytecode/thread/multi/AddRunnable3.java
@@ -0,0 +1,50 @@
+package hxy.bytecode.thread.multi;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+
+/**
+ * @author eric
+ * @program bytecode
+ * @description \
+ * @date 2021/5/15
+ */
+public class AddRunnable3 implements Runnable {
+    List<Integer> list;
+    CountDownLatch countDownLatch;
+
+    AddRunnable3(List list) {
+        this.list = list;
+    }
+
+    AddRunnable3(List list, CountDownLatch countDownLatch) {
+        this.list = list;
+        this.countDownLatch = countDownLatch;
+    }
+
+    @Override
+    public void run() {
+        for (int i = 0; i < 100000; i++) {
+            list.add(i);
+        }
+        System.out.println(list.size());
+        countDownLatch.countDown();
+    }
+
+    public static void main(String[] args) {
+        ArrayList<Integer> objects = new ArrayList<>();
+        final CountDownLatch countDownLatch = new CountDownLatch(2);
+
+        new Thread(new AddRunnable3(objects,countDownLatch), "线程1").start();
+        new Thread(new AddRunnable3(objects,countDownLatch), "线程2").start();
+
+        try {
+            countDownLatch.await();
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+        System.out.println(objects.size());
+
+    }
+}
diff --git a/src/main/java/hxy/bytecode/thread/multi/AddThread.java b/src/main/java/hxy/bytecode/thread/multi/AddThread.java
new file mode 100644
index 0000000000000000000000000000000000000000..8a03c00af838f25c3fecc2eb33e5576c8cfcf4f6
--- /dev/null
+++ b/src/main/java/hxy/bytecode/thread/multi/AddThread.java
@@ -0,0 +1,15 @@
+package hxy.bytecode.thread.multi;
+
+/**
+ * @author eric
+ * @program bytecode
+ * @description
+ * @date 2021/5/15
+ */
+public class AddThread extends Thread {
+    @Override
+    public void run() {
+
+
+    }
+}
diff --git a/src/test/java/hxy/bytecode/ArrayMove.java b/src/test/java/hxy/bytecode/ArrayMove.java
new file mode 100644
index 0000000000000000000000000000000000000000..9218cff36f141aa56f7837bbc8ea1883b8e9bd92
--- /dev/null
+++ b/src/test/java/hxy/bytecode/ArrayMove.java
@@ -0,0 +1,40 @@
+package hxy.bytecode;
+
+import java.util.Arrays;
+
+/**
+ * @author eric
+ * @program bytecode
+ * @description 给定一个整数数组，把0挪到最后，其他数字的顺序不变。要求时间复杂度为1. 两两交换
+ * @date 2021/6/27
+ */
+public class ArrayMove {
+    public static void main(String[] args) {
+        int[] array = new int[]{1, 2, 0, 4, 5, 0, 6, 7, 9};
+        int index2;
+        for (int i = 0; i < array.length; i++) {
+            if (array[i] == 0) {
+                // 查找下一个不为0的数组下标交换下。
+                index2 = i;
+                if (index2 < array.length - 1) {
+                    while (array[index2] == 0) {
+                        index2++;
+                        if (index2 >= array.length) {
+                            break;
+                        }
+                    }
+                    if (index2 <= array.length - 1) {
+                        int temp = array[index2];
+                        array[index2] = array[i];
+                        array[i] = temp;
+                    }
+                }
+                index2++;
+            }
+        }
+        final int[] ints = Arrays.stream(array).toArray();
+        for (int i = 0; i < ints.length; i++) {
+            System.out.print(ints[i]);
+        }
+    }
+}