java_collection

#Java collection framework
The core collection interfaces are the foundation of the Java Collections Framework.

The Java Collections Framework hierarchy consists of two distinct interface trees:

The first tree starts with the Collection interface, which provides for the basic functionality used by all collections, such as add and remove methods. Its subinterfaces — Set, List, and Queue — provide for more specialized collections.

The Set interface does not allow duplicate elements. This can be useful for storing collections such as a deck of cards or student records. The Set interface has a subinterface, SortedSet, that provides for ordering of elements in the set.

The List interface provides for an ordered collection, for situations in which you need precise control over where each element is inserted. You can retrieve elements from a List by their exact position.

The Queue interface enables additional insertion, extraction, and inspection operations. Elements in a Queue are typically ordered in on a FIFO basis.

The Deque interface enables insertion, deletion, and inspection operations at both the ends. Elements in a Deque can be used in both LIFO and FIFO.

The second tree starts with the Map interface, which maps keys and values similar to a Hashtable.

Map’s subinterface, SortedMap, maintains its key-value pairs in ascending order or in an order specified by a Comparator.

These interfaces allow collections to be manipulated independently of the details of their representation.

##Collection

###List

1. ArrayList: 内部使用动态数组来实现，当调用add/remove等方法时，会拷贝数组
2. LinkedList: 内部使用双向链表实现，当调用set/get等方法时，需要遍历

###Set

1. HashSet: 内部使用hashMap来实现, 利用其key值不能重复的特点
2. LinkedHashSet: 内部使用LinkedHashMap来实现，它的特点是可以按插入顺序遍历
3. TreeSet: 内部使用TreeMap来实现，它保证set处于排序状态
4. SortedSet: 集合内部的元素可以按照一定的顺序进行排序，内部通常借助sortedMap实现

可以看出，set的实现大多依赖于Map, 不同的set实现主要是由于内部使用的map类型不同

###Queue

1. BlockingQueue: 阻塞式队列，包括ArrayBlockingQueue和LinkedBlockingQueue
2. Deque: 双向队列，可以用来实现栈, ArrayDeque, LinkedList
3. BlockingDeque: 阻塞式双向队列, LinkedBlockingDeque

##Map

1. HashMap: 使用key-value的值进行存储， 这是非同步的(Hashtable是同步的)
2. LinkedHashMap: 使用链表的方式进行存储，它可以按插入的顺序进行输出
3. TreeMap: 它可以按照指定的比较器进行排序输出
4. SortedMap: 按照一定的比较器对结果进行输出，TreeMap是它的一种实现
5. ConcurrentMap: map的多线程实现，它将map分成多个（默认是16个）hashtable，在每个hashtable中可同时进行操作

###Arrays

1. asList: 将数组转化成List对象
2. binarySearch: 二分查找
3. sort: 排序
4. fill: 填充
5. copyOf: 拷贝

###Collections

1. Sorting
2. shuffling
3. routing data
4. searching
5. composition