1.数组将数字和对象联系起来，保存类型明确的对象。一旦生成，容量不可改变
2.Collection保存单一的元素，Map保存相关联的键值对。有了java的泛型，你就可以指定容器中存放的对象类型，因此你就不会将错误类型的对象放置到容器中，并且在从容器中获取元素时，不必进行类型转化。容器不可以持有基本类型，但自动包装机制会仔细的执行基本类型到容器中所持有的包装器类型的双向转换
3.List也建立数字索引和对象的关联，和数组类似，但list可以自动扩容。
4.ArrayList：大量随机访问，LinkedList:表中插入或删除元素，使用LinkedList。
5Queue和栈有LinkedList提供支持。
6Map将对象与对象相关联，HashMap设计用来快速访问；TreeMap保持“键”始终处于排序状态，所以没有HashMap快。LinkedHashMap保持元素插入的顺序，但也提供了快速访问的能力。
7Set不接受重复元素，HashSet提供最快的查询速度，TreeSet保持元素处于排序状态。LinkedHashSet以插入顺序保存元素
类与接口中所实现的接口
Collection: [add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray]
Interfaces in Collection: [Iterable]
Set extends Collection, adds: []
Interfaces in Set: [Collection]
HashSet extends Set, adds: []
Interfaces in HashSet: [Set, Cloneable, Serializable]
LinkedHashSet extends HashSet, adds: []
Interfaces in LinkedHashSet: [Set, Cloneable, Serializable]
TreeSet extends Set, adds: [pollLast, navigableHeadSet, descendingIterator, lower, headSet, ceiling, pollFirst, subSet, navigableTailSet, comparator, first, floor, last, navigableSubSet, higher, tailSet]
Interfaces in TreeSet: [NavigableSet, Cloneable, Serializable]
List extends Collection, adds: [listIterator, indexOf, get, subList, set, lastIndexOf]
Interfaces in List: [Collection]
ArrayList extends List, adds: [ensureCapacity, trimToSize]
Interfaces in ArrayList: [List, RandomAccess, Cloneable, Serializable]
LinkedList extends List, adds: [pollLast, offer, descendingIterator, addFirst, peekLast, removeFirst, peekFirst, removeLast, getLast, pollFirst, pop, poll, addLast, removeFirstOccurrence, getFirst, element, peek, offerLast, push, offerFirst, removeLastOccurrence]
Interfaces in LinkedList: [List, Deque, Cloneable, Serializable]
Queue extends Collection, adds: [offer, element, peek, poll]
Interfaces in Queue: [Collection]
PriorityQueue extends Queue, adds: [comparator]
Interfaces in PriorityQueue: [Serializable]
Map: [clear, containsKey, containsValue, entrySet, equals, get, hashCode, isEmpty, keySet, put, putAll, remove, size, values]
HashMap extends Map, adds: []
Interfaces in HashMap: [Map, Cloneable, Serializable]
LinkedHashMap extends HashMap, adds: []
Interfaces in LinkedHashMap: [Map]
SortedMap extends Map, adds: [subMap, comparator, firstKey, lastKey, headMap, tailMap]
Interfaces in SortedMap: [Map]
TreeMap extends Map, adds: [descendingEntrySet, subMap, pollLastEntry, lastKey, floorEntry, lastEntry, lowerKey, navigableHeadMap, navigableTailMap, descendingKeySet, tailMap, ceilingEntry, higherKey, pollFirstEntry, comparator, firstKey, floorKey, higherEntry, firstEntry, navigableSubMap, headMap, lowerEntry, ceilingKey]
Interfaces in TreeMap: [NavigableMap, Cloneable, Serializable]