Summary Map:c++ V.s. Java

Organize the map in Java and C + + basic operations, we welcome you to exchange learning.

Attached: for C + +, choose Map or Unordered_map, you can refer to this discussion. The relatively simple and crude conclusion is that UNORDERED_MAP is faster because UNORDERED_MAP uses a hash table internally, and map uses the structure of a red-black tree internally, so for the lookup operation, the former is O (1), which is actually O (LgN).

Main differences:

1. C + + in the main can be used [] to operate (add,update,access); Java is not [], the corresponding action is put (Key,value), get (key)
2. For a key lookup, C + + uses Iteator iterator operations, using ContainsKey (key) in Java

	C++	Java	Describe
Structure	Unordered_map<string,int>salary	map<string, integer> salarymap = new hashmap<string, integer> ();
Increase	Salary["Tom"] = 10;	Salarymap. put ("Tom", 10);	Update: If there is Join: If not present
Delete	Salary. Erase ("Tom");	Salary. Remove ("Tom");	If it does not exist, ignore
Find	if (Salary.find ("Tom")! = Salary.end ()) { cout << "Tom:" << salary["Tom"]; }	if (Salarymap.containskey ("Tom")) { System.out.println ("Tom:" + Salarymap.get ("Tom")); }	Use Key to query
Modify	salary["Tom"] = 20;	Salarymap.put ("Tom", 20);
Capacity	Salary.size (); Salary. Empty ();	Salarymap.size (); Salarymap. IsEmpty ();
Clear	Salary.clear ();	Salary.clear ()
Reference	#include <unordered_map>	Import Java.util.Map; Import Java.util.HashMap;

Summary Map:c++ V.s. Java