A. Set
The disorder can not be repeated
Disorder: storage order and get a different order
HashSet: data structure is a hash table
TreeSet: binary tree
Two. Map
One to one mapping between (key-value pairs)
Unique key value may be repeated
2.1 Create
format:
Map <key type, value type> set name = new HashMap <> ();
2.2 common method
1, put (e1, e2): The e1, e2 form a key to the storage to the collection; e1 if the key does not exist, null is returned, otherwise, the return value is covered
2, remove (key): the key corresponding to the key deletion, the return value is deleted, if the key does not exist, return null
3, remove (key, value): holding a key in a map to find whether there is the key, if the key does not exist, false is returned delete failed; if this is the same key value exists and the key corresponding to the incoming value Removes and returns true, and vice versa false.
4, replace (key, value): If the key does not exist, or null replaced; if you will replace the old value of the value of this key
5, replace (key, oldValue, newValue): with logic remove (key, value), but the function performed is to replace the
6, get (key): Get values corresponding to the key, this key does not exist return null
7、containValue(value)
8、containKey(key)
9、isEmpty()
10、clear()
11、size()
12, values (): returns the value of a collection of Collection
13, a.putAll (b): The b added to a set of collection, if the key exists already covered