fix: get(index) in array list

close #152

Author: yanglbme

docs/JDK/collection/ArrayList.md

@@ -159,8 +159,8 @@ public void set(E e) {
 ```java
 public E get(int index) {
     rangeCheck(index);
-    checkForComodification();
-    return ArrayList.this.elementData(offset + index);
+
+    return elementData(index);
 }
 ```