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diff --git a/notes/Java 容器.md b/notes/Java 容器.md
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--- a/notes/Java 容器.md	
+++ b/notes/Java 容器.md	
@@ -255,6 +255,31 @@ List<String> synList = Collections.synchronizedList(list);
 List<String> list = new CopyOnWriteArrayList<>();
 ```
 
+扩展：CopyOnWriteArrayList是一种CopyOnWrite容器，即写时复制的容器。从以下源码中看出：当向容器中添加元素时，不是直接往当前容器添加，而是Copy当前容器，在新容器中添加，添加完后，将原容器的引用指向新容器。这样做可以对CopyOnWrite容器进行并发的读，不需要加锁，极大地提高了读性能，因此适用于读多写少的场景。
+
+```java
+public boolean add(E e) {
+	final ReentrantLock lock = this.lock;
+    lock.lock();
+    try {
+        Object[] elements = getArray();
+        int len = elements.length;
+        Object[] newElements = Arrays.copyOf(elements, len + 1); // 复制到新容器
+        newElements[len] = e;
+        setArray(newElements);
+        return true;
+    } finally {
+        lock.unlock();
+    }
+}
+
+@SuppressWarnings("unchecked")
+private E get(Object[] a, int index) {
+    return (E) a[index];
+}
+
+```
+
 ## LinkedList
 
 ### 1. 概览