SendableLruCache<K, V>

Provides APIs to discard the least recently used data to make rooms for new elements when the cache is full. This class uses the Least Recently Used (LRU) algorithm, which believes that the recently used data may be accessed again in the near future and the least accessed data is the least valuable data and should be removed from the cache. SendableLruCache supports the Sendable feature, allowing it to store Sendable objects and ensuring safe cross-thread access.

NOTE

The initial APIs of this module are supported since API version 12. Newly added APIs will be marked with a superscript to indicate their earliest API version.

The initial SendableLruCache APIs are supported since API version 18.

This module can be imported only to ArkTS files (with the file name extension .ets).

Modules to Import

import { ArkTSUtils } from '@kit.ArkTS'

Properties

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Name	Type	Read-Only	Optional	Description
length¹⁸⁺	number	Yes	No	Total number of values in this cache.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
pro.put(1, 8);
let result = pro.length;
console.info('result = ' + result);
// Expected output: result = 2

constructor¹⁸⁺

constructor(capacity?: number)

A constructor used to create a SendableLruCache instance. The default capacity of the cache is 64.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
capacity	number	No	Capacity of the cache to create. The default value is 64, and the maximum value is 2147483647. If the value is less than or equal to 0, an exception is thrown.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();

updateCapacity¹⁸⁺

updateCapacity(newCapacity: number): void

Changes the cache capacity. If the total number of values in the cache exceeds the specified capacity, the least recently used key-value pairs are removed.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
newCapacity	number	Yes	New capacity of the cache. The maximum value is 2147483647. If the value is less than or equal to 0, an exception is thrown.

Error codes

For details about the error codes, see Universal Error Codes.

ID	Error Message
401	Parameter error. Possible causes: 1.Mandatory parameters are left unspecified;2.Incorrect parameter types.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.updateCapacity(100);

toString¹⁸⁺

toString(): string

Obtains the string representation of this cache.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
string	String representation of the cache, in the format of SendableLruCache[ maxSize = (maxSize), hits = (hitCount), misses = (missCount), hitRate = (hitRate) ], where (maxSize) indicates the maximum size of the cache, (hitCount) indicates the number of matched queries, (missCount) indicates the number of times that the number of mismatched queries, and (hitRate) indicates the matching rate.

Type

Description

string

String representation of the cache, in the format of SendableLruCache[ maxSize = (maxSize), hits = (hitCount), misses = (missCount), hitRate = (hitRate) ], where (maxSize) indicates the maximum size of the cache, (hitCount) indicates the number of matched queries, (missCount) indicates the number of times that the number of mismatched queries, and (hitRate) indicates the matching rate.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
pro.get(2);
pro.get(3);
console.info(pro.toString());
// Expected output: SendableLruCache[ maxSize = 64, hits = 1, misses = 1, hitRate = 50% ]
// maxSize: maximum size of the cache. hits: number of matched queries. misses: number of mismatched queries. hitRate: matching rate.

getCapacity¹⁸⁺

getCapacity(): number

Obtains the capacity of this cache.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
number	Capacity of the cache.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
let result = pro.getCapacity();
console.info('result = ' + result);
// Expected output: result = 64

clear¹⁸⁺

clear(): void

Clears all key-value pairs from this cache.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
let result = pro.length;
pro.clear();
let res = pro.length;
console.info('result = ' + result);
console.info('res = ' + res);
// Expected output: result = 1
// Expected output: res = 0

getCreateCount¹⁸⁺

getCreateCount(): number

Obtains the number of times that the default internal API is called to create objects.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
number	Number of times that the default internal API is called.

Example

@Sendable
class ChildLRUCache extends ArkTSUtils.SendableLruCache<number, number> {
  constructor() {
    super();
  }
  createDefault(key: number): number {
    return key;
  }
}

let lru = new ChildLRUCache();
lru.put(2, 10);
lru.get(3);
lru.get(5);
let res = lru.getCreateCount();
console.info('res = ' + res);
// Expected output: res = 2
// When the get operation is performed, if the key does not exist, call the createDefault API to check whether the return value is undefined.
// If the return value is not undefined, add the key and return value to the cache as a new entry and increase the creation count by one.

getMissCount¹⁸⁺

getMissCount(): number

Obtains the number of times that the queried values are mismatched.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
number	Number of times that the queried values are mismatched.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
pro.get(2);
let result = pro.getMissCount();
console.info('result = ' + result);
// Expected output: result = 0

getRemoveCount¹⁸⁺

getRemoveCount(): number

Obtains the number of times that key-value pairs in the cache are recycled. When the size of the cache exceeds the capacity limit, the least used key-value pairs will be recycled.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
number	Number of times that key-value pairs in the cache are recycled.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
pro.updateCapacity(2);
pro.put(50, 22);
let result = pro.getRemoveCount();
console.info('result = ' + result);
// Expected output: result = 0

getMatchCount¹⁸⁺

getMatchCount(): number

Obtains the number of times that the queried values are matched.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
number	Number of times that the queried values are matched.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
pro.get(2);
let result = pro.getMatchCount();
console.info('result = ' + result);
// Expected output: result = 1

getPutCount¹⁸⁺

getPutCount(): number

Obtains the number of additions to this cache.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
number	Number of additions to the cache.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
let result = pro.getPutCount();
console.info('result = ' + result);
// Expected output: result = 1

isEmpty¹⁸⁺

isEmpty(): boolean

Checks whether this cache is empty.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
boolean	Check result. The value true is returned if the cache is empty and does not contain any key-value pairs; otherwise, false is returned.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
let result = pro.isEmpty();
console.info('result = ' + result);
// Expected output: result = false

get¹⁸⁺

get(key: K): V|undefined

Obtains the value of a key.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
key	K	Yes	Key based on which the value is queried.

Return value

Type	Description
V \|undefined	If the specified key exists in the cache, the return value is the value associated with that key. If not, the default internal API is called to generate an object with the same key and value and return the value. If the default internal API returns undefined, the return value is undefined; otherwise, the return value is whatever that API comes up with.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
let result  = pro.get(2);
console.info('result = ' + result);
// Expected output: result = 10

put¹⁸⁺

put(key: K,value: V): V

Adds a key-value pair to this cache and returns the value associated with the key. If the total number of values in the cache is greater than the specified capacity, the deletion operation is performed.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
key	K	Yes	Key of the key-value pair to add.
value	V	Yes	Value of the key-value pair to add.

Return value

Type	Description
V	Value of the key-value pair added.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
let result = pro.put(2, 10);
console.info('result = ' + result);
// Expected output: result = 10

values¹⁸⁺

values(): V[]

Obtains all values in this cache, listed from the most to the least recently accessed, where the most recently accessed indicates the key-value pair with the latest operation.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
V []	All values in the cache, listed from the most to the least recently used.

Example

let pro = new ArkTSUtils.SendableLruCache<number|string,number|string>();
pro.put(2, 10);
pro.put(2, "anhu");
pro.put("afaf", "grfb");
let result = pro.values();
console.info('result = ' + result);
// Expected output: result = anhu,grfb

keys¹⁸⁺

keys(): K[]

Obtains all keys in this cache, listed from the most to the least recently accessed.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
K []	All keys in the cache, listed from the most to the least recently used.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
pro.put(3, 1);
let result = pro.keys();
console.info('result = ' + result);
// Expected output: result = 2,3

remove¹⁸⁺

remove(key: K): V|undefined

Removes a key and its associated value from this cache and returns the value associated with the key. If the key does not exist, undefined is returned.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
key	K	Yes	Key to remove.

Return value

Type	Description
V \| undefined	Returns an Optional object containing the removed key-value pair if the key exists in the cache; returns undefined if the key does not exist; throws an error if null is passed in for key.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
let result = pro.remove(20);
console.info('result = ' + result);
// Expected output: result = undefined

contains¹⁸⁺

contains(key: K): boolean

Checks whether the cache contains the specified key.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
key	K	Yes	Key to check.

Return value

Type	Description
boolean	Check result. The value true is returned if the cache contains the specified key; otherwise, false is returned.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
let result = pro.contains(2);
console.info('result = ' + result);
// Expected output: result = true

entries¹⁸⁺

entries(): IterableIterator<[K,V]>

Obtains a new iterator object that contains all key-value pairs in this object.

Atomic service API: This API can be used in atomic services since API version 18.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
IterableIterator<[K, V]>	Iterable array.

Example

let pro = new ArkTSUtils.SendableLruCache<number, number>();
pro.put(2, 10);
pro.put(3, 15);
let pair:Iterable<Object[]> = pro.entries();
let arrayValue = Array.from(pair);
for (let value of arrayValue) {
  console.info(value[0]+ ', '+ value[1]);
  // Expected output:
  // 2, 10
  // 3, 15
}

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SendableLruCache<K, V>

Modules to Import

Properties

constructor¹⁸⁺

updateCapacity¹⁸⁺

toString¹⁸⁺

getCapacity¹⁸⁺

clear¹⁸⁺

getCreateCount¹⁸⁺

getMissCount¹⁸⁺

getRemoveCount¹⁸⁺

getMatchCount¹⁸⁺

getPutCount¹⁸⁺

isEmpty¹⁸⁺

get¹⁸⁺

put¹⁸⁺

values¹⁸⁺

keys¹⁸⁺

remove¹⁸⁺

contains¹⁸⁺

entries¹⁸⁺

你可能感兴趣的鸿蒙文章

标签云

最热博客

最新博客

SendableLruCache<K, V>

Modules to Import

Properties

constructor18+

updateCapacity18+

toString18+

getCapacity18+

clear18+

getCreateCount18+

getMissCount18+

getRemoveCount18+

getMatchCount18+

getPutCount18+

isEmpty18+

get18+

put18+

values18+

keys18+

remove18+

contains18+

entries18+

你可能感兴趣的鸿蒙文章

标签云

最热博客

最新博客

constructor¹⁸⁺

updateCapacity¹⁸⁺

toString¹⁸⁺

getCapacity¹⁸⁺

clear¹⁸⁺

getCreateCount¹⁸⁺

getMissCount¹⁸⁺

getRemoveCount¹⁸⁺

getMatchCount¹⁸⁺

getPutCount¹⁸⁺

isEmpty¹⁸⁺

get¹⁸⁺

put¹⁸⁺

values¹⁸⁺

keys¹⁸⁺

remove¹⁸⁺

contains¹⁸⁺

entries¹⁸⁺