map
In different languages, "map" has many different names. The "map" in Z1h corresponds to the following languages. The names of the same concepts are similar:
| language | name | characteristics or main differences |
|:-:|:-:|:-:|
Z1h | map | Unordered, thread unsafe |
Z1h | Map | Unordered, thread safe |
Go | map [string] interface {} | Assignment is not allowed through s.key = value, Only s ["key"] is allowed to operate |
Python | set (set) | Assignment is not allowed through s.key = value, only s ["key"] is allowed to operate |
JavaScript | Object | No s ?. key for optional chain operation |
Java | HashMap
Declare to
create a map method:
// Thread-unsafe map
// Create an empty map
m1 = {}
// Initialize the constant content
m2 = {"name": "z"}
// During initialization, the key can omit the string identifier (', ", \ `)
m3 = {name:" z "}
// At initialization,When key and variable name are the same,
m4 = {m3}
// thread-safe map
// Initialize a multi-thread-safe map
m5 = new (sync.Map)
// Initialize a thread-safe map with a limited number of keys and automatically eliminate unpopular keys
m6 = new ("weak")
m7 = new ("weak" , 2) // The number of keys is limited to a maximum of 2, triggering elimination when more than two
// Initialize a thread-safe map with expired elimination mechanism
m8 = new ("expire")
m9 = new ("expire", 3) / The default expiration time of the / key is 3 seconds
m10 = new ("expire", new ("weak")) // execute two elimination strategies at the same time
In addition there are methods to generate
// from the string Convert to map
m11 = JSON.parse (`{" name ":" zzz "}`)
Assignment
can be done in the following ways
- map variable name **. ** key = value
- map variable name [key] = value
Example:
m = {
name: "z",
};
m.age = 18; // Set age
m ["tall"] = 171 ;// Set tall
key = "weight";
m [key] = 61.5; // Set weight
print (m);
The
above example will
output
{"age": 18, "name": "z", "tall": 171, "weight ": 61.5}
The value
can be obtained from the map in the following ways-
map
variable name **. **key - map variable name [key]
-{key1, key2} = Variable name inherits the
above environment:
print ("Name:", m ["name"]);
print ("Height:", m.tall);
{age, weight} = m;
print (`Age: $ (age), Weight: $ (weight)`);
The
above example will
output
Name: z
Height: 171
Age: 18, Weight: 61.5
Optional
If the key does not exist when the chain tries to value the map, a Not In error will be thrown. At this time, there are two ways to judge and value
-has (map variable name, key) // return bool type
-map variable name ?. key // If the key does not exist, return nil
-map variable name ?[key variable]// If the key does not exist, return nil to
inherit the above environment:
print (has (m, "name")); // true
print (m? .name); // z
print (has (m, "gender")); // false
print (m? .gender); // null
print (m? ["score"]); // null
Post-incremental increment and decrement increment
a key of the map, for example
m.age ++; // 19
m ["age"] ++ // 20
m.weight--; / / 60.5
m [ "weight"] -; // 59.5
If a thread safe map, count may be incremented to a non-existent Key
m.score ++; //. 1
m ["score"] ++ // 2
remove key
** Thread unsafe map ** delete method is as follows:
del (m, "age");
key = "score" ;
del (m, key);
** The thread-safe Map ** deletion method is as follows:
m.Delete (" age ");
key =" score ";
m.Delete (" age ");
Serialize the
following methods to ** to convert to a thread-safe string ** Map - the JSON.stringify (m); - string (m);
acquires a list of key
Object.keys (m)
list acquisition value
Object.values (m)
traversing
@ mode. 1
for (K, V in m) {
Print ( Key $ = {K}, the Value = '$ {V})
} ;
// Method 2
Object.keys (m) .forEach (k => {
print (Key = $ {k}, Value = $ (m [k]})
});
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