[A] list: ArrayList

Author: c-rainstorm

README.md

@@ -48,7 +48,8 @@
         │   ├── <a href="./java/source-code/">source-code</a><br>
         │   │   └── <a href="./java/source-code/jdk/">jdk</a><br>
         │   │   &nbsp;&nbsp;&nbsp; ├── <a href="./java/source-code/jdk/collection/">collection</a><br>
-        │   │   &nbsp;&nbsp;&nbsp; │   └── <a href="./java/source-code/jdk/collection/collection.md">collection.md</a><br>
+        │   │   &nbsp;&nbsp;&nbsp; │   ├── <a href="./java/source-code/jdk/collection/collection.md">collection.md</a><br>
+        │   │   &nbsp;&nbsp;&nbsp; │   └── <a href="./java/source-code/jdk/collection/list-arraylist.md">list-arraylist.md</a><br>
         │   │   &nbsp;&nbsp;&nbsp; └── <a href="./java/source-code/jdk/lang/">lang</a><br>
         │   │   &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; └── <a href="./java/source-code/jdk/lang/integer.md">integer.md</a><br>
         │   ├── <a href="./java/test/">test</a><br>

java/source-code/jdk/collection/list-arraylist.md

@@ -0,0 +1,89 @@
+# ArrayList
+
+## 最大数组容量
+
+> 有两种限制。
+>
+> 一是规范隐含的限制。
+>
+> Java数组的length必须是非负的int，
+>
+> 所以它的理论最大值就是java.lang.Integer.MAX_VALUE = 2^31-1 = 2147483647。
+>
+> 二是具体的实现带来的限制。
+>
+> 这会使得实际的JVM不一定能支持上面说的理论上的最大length。例如说如果有JVM使用uint32_t来记录对象大小的话，那可以允许的最大的数组长度（按元素的个数计算）就会是：
+>
+> (uint32_t的最大值 - 数组对象的对象头大小) / 数组元素大小
+>
+> 于是对于元素类型不同的数组，实际能创建的数组的最大length也会不同。JVM实现里可以有许多类似的例子会影响实际能创建的数组大小。
+
+作者：RednaxelaFX
+链接：https://www.zhihu.com/question/31809233/answer/53370790
+来源：知乎
+著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
+
+> The **count** must be of type int.
+>
+> if count is less than zero, the anewarray instruction throws a NegativeArraySizeException.
+>
+> [anewarray - Java Virtual Machine Specification][anewarray]
+
+## 数组容量自增
+
+```java
+/**
+    * The maximum size of array to allocate.
+    * Some VMs reserve some header words in an array.
+    * Attempts to allocate larger arrays may result in
+    * OutOfMemoryError: Requested array size exceeds VM limit
+    */
+private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
+
+private void grow(int minCapacity) {
+    // overflow-conscious code
+    int oldCapacity = elementData.length;
+    // 正常一次扩容为原容量的 3/2
+    int newCapacity = oldCapacity + (oldCapacity >> 1);
+    if (newCapacity - minCapacity < 0)
+        // 新容量溢出，或者新容量依旧没有达到 minCapacity
+        newCapacity = minCapacity;
+    if (newCapacity - MAX_ARRAY_SIZE > 0)
+        newCapacity = hugeCapacity(minCapacity);
+    // minCapacity is usually close to size, so this is a win:
+    elementData = Arrays.copyOf(elementData, newCapacity);
+}
+
+private static int hugeCapacity(int minCapacity) {
+    if (minCapacity < 0) // overflow
+        throw new OutOfMemoryError();
+    return (minCapacity > MAX_ARRAY_SIZE) ?
+        Integer.MAX_VALUE :
+        MAX_ARRAY_SIZE;
+}
+```
+
+## 开源组件拓展
+
+### `UidGenerator` 环形缓存
+
+![CachedUidGenerator - 双RingBuffer](http://image.rainstorm.vip/blog/ringbuffer.png)
+
+`@see` [UidGenerator][UidGenerator]
+
+### `Disruptor` 高性能队列
+
+// todo
+
+## 参考
+
+- [知乎: Java 数组有最大长度吗？ - 作者：RednaxelaFX](https://www.zhihu.com/question/31809233/answer/53370790)
+- [anewarray - Java Virtual Machine Specification][anewarray]
+- [关于面试题“ArrayList循环remove()要用Iterator”的研究 - since1986](https://juejin.im/post/59ef1ab0518825619a01e00a)
+- [《我们一起进大厂》系列-ArrayList - 敖丙](https://juejin.im/post/5e14b51d5188253a9a213e83)
+- [Java集合框架常见面试题 - JavaGuide](https://github.com/Snailclimb/JavaGuide/blob/master/docs/java/collection/Java%E9%9B%86%E5%90%88%E6%A1%86%E6%9E%B6%E5%B8%B8%E8%A7%81%E9%9D%A2%E8%AF%95%E9%A2%98.md#%E8%A1%A5%E5%85%85%E5%86%85%E5%AE%B9randomaccess%E6%8E%A5%E5%8F%A3)
+- [Core algorithms deployed](https://cstheory.stackexchange.com/questions/19759/core-algorithms-deployed/19773#19773)
+- [UidGenerator][UidGenerator]
+
+[anewarray]: https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-6.html#jvms-6.5.anewarray
+[UidGenerator]: https://github.com/baidu/uid-generator/blob/master/README.zh_cn.md