The Clollections API 集合API

The ArrarList class is in the clollection API （applictation programming interface), whick is a library provided by Java.Most of the API in java.util . This library gives the programmer access to prepackaged data staructures and the methods to manipulate them . The implementations of these container classes are invisible and should not be of concren to the programmer . The code works . And it is reusable .

All of the collections classes ,including ArrayList , hava thefollowing features int commons:

• They are designed to be both memory and run-time efficient.
• They provide methods for insertion and removal of items (i.e., they can grow and shrink).

• They provide for iteration over the entire collection