Learning map in Java (describes the usage of MAP and iterator in Java)

Q: If it is more appropriate to put data in map, it is more special to put data in other containers;

Map is a key-value correspondence. I know. I want to know under what circumstances can I use a key-value pair or an array or another two-dimensional container?

A: Java model.
I will give you some of my previous student representatives.
1 import java. util. Map;
2 Import java. util. hashmap;
3 Import java. util. hashset;
4 Import java. util. Set;
5 import java. util. iterator;
6
7
8 class hashmaptest {
9
10
11 public static void main (string [] ARGs ){
12
13 Map <string, string> map = new hashmap <string, string> ();

14 map. Put ("key1", "value1 ");
15 map. Put ("key2", "hashmap value2 ");
16
17 system. Out. println (Map. Get ("key2 "));
18
19 set <string> set = new hashset <string> ();

20 set. Add ("this is hashset test1 ");

21 set. Add ("this is hashset Test2 ");

22
23
24
25 iterator <string> iter = set. iterator ();

26 while (ITER. hasnext ()){
27 system. Out. println (ITER. Next ());

28}
29 for (string STR: Set ){
30 system. Out. println (STR );
31}
32
33
34}
35}

A: While map will automatically help you complete the search

A: similar to functions in mathematics, for example, y = f (x). Based on X, we can determine that the value of Y in map is

Map. Put ("X", "Y ");
Map. Get ("X") = y
It is actually a one-to-one ing relationship.

Key ------ Value

Each key corresponds to a value and the key knows the value.

2q: How does one obtain its value through the map key in Java?

A: object OBJ = new object ();
OBJ = map. Get ("key ");
Map is the object of map, and "key" is the value of key, which is generally a string.

A: Use the get (Object key) method to obtain

A: Map <string, string> maps = new hashmap <string, string> ();
// Obtain the set of keys
Set <string> keyset = maps. keyset ();
// Traverses the key set and obtains the value
For (string key: keyset ){
String value = maps. Get (key );
}