@ohos.util.LightWeightSet (Nonlinear Container LightWeightSet)

LightWeightSet stores a set of values, each of which must be unique.

LightWeightSet is based on generics and uses a lightweight structure. Its default initial capacity is 8, and it has the capacity doubled in each expansion.

The values in such a set are searched using hash values, which are stored in an array.

Compared with HashSet, which can also store values, LightWeightSet occupies less memory.

Recommended use case: Use LightWeightSet when you need a set that has only unique elements or need to deduplicate a set.

This topic uses the following to identify the use of generics: - T: Type

NOTE

The initial APIs of this module are supported since API version 8. Newly added APIs will be marked with a superscript to indicate their earliest API version.

Modules to Import

import { LightWeightSet } from '@kit.ArkTS';

LightWeightSet

Attributes

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

constructor

constructor()

A constructor used to create a LightWeightSet instance.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

let lightWeightSet: LightWeightSet<number|string> = new LightWeightSet();

isEmpty

isEmpty(): boolean

Checks whether this container is empty (contains no element).

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

const lightWeightSet: LightWeightSet<number> = new LightWeightSet();
let result = lightWeightSet.isEmpty();

add

add(obj: T): boolean

Adds an element to this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
let result = lightWeightSet.add("squirrel");

addAll

addAll(set: LightWeightSet<T>): boolean

Adds all elements in a LightWeightSet instance to this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let set: LightWeightSet<string> = new LightWeightSet();
set.add("gull");
let result = lightWeightSet.addAll(set);

hasAll

hasAll(set: LightWeightSet<T>): boolean

Checks whether this container contains all elements of the specified LightWeightSet instance.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let set: LightWeightSet<string> = new LightWeightSet();
set.add("sparrow");
let result = lightWeightSet.hasAll(set);

has

has(key: T): boolean

Checks whether this container has the specified key.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<number> = new LightWeightSet();
lightWeightSet.add(123);
let result = lightWeightSet.has(123);

increaseCapacityTo

increaseCapacityTo(minimumCapacity: number): void

Increases the capacity of this container.

If the passed-in capacity is greater than or equal to the number of elements in this container, the container capacity is changed to the new capacity. If the passed-in capacity is less than the number of elements in this container, the capacity is not changed.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.increaseCapacityTo(10);

getIndexOf

getIndexOf(key: T): number

Obtains the position index of the element with the specified key in this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let result = lightWeightSet.getIndexOf("sparrow");

remove

remove(key: T): T

Removes an element of the specified key from this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let result = lightWeightSet.remove("sparrow");

removeAt

removeAt(index: number): boolean

Removes the element at the specified position from this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let result = lightWeightSet.removeAt(1);

getValueAt

getValueAt(index: number): T

Obtains the value of the element at the specified position in this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Parameters

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let result = lightWeightSet.getValueAt(1);

clear

clear(): void

Clears this container and sets its length to 0.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
lightWeightSet.clear();

toString

toString(): String

Obtains a string that contains all elements in this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let result = lightWeightSet.toString();

toArray

toArray(): Array<T>

Obtains an array that contains all objects in this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let result = lightWeightSet.toArray();

values

values(): IterableIterator<T>

Obtains an iterator that contains all the values in this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let iter = lightWeightSet.values();
let index = 0;
while(index < lightWeightSet.length) {
  console.log(JSON.stringify(iter.next().value));
  index++;
}

forEach

forEach(callbackFn: (value?: T, key?: T, set?: LightWeightSet<T>) => void, thisArg?: Object): void

Uses a callback to traverse the elements in this container and obtain their position indexes.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

callbackFn |Name|Type|Mandatory|Description| |——–|——–|——–|——–| |value|T|No|Value of the element that is currently traversed. The default value is the value of the first key-value pair.| |key|T|No|Key of the element that is currently traversed (same as value). The default value is the key of the first key-value pair.| |set|LightWeightSet<T>|No|Instance that calls the forEach API. The default value is this instance.|

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("sparrow");
lightWeightSet.add("gull");
lightWeightSet.forEach((value ?: string, key ?: string) => {
  console.log("value:" + value, "key:" + key);
});

// You are not advised to use the add, remove, or removeAt APIs in forEach because they may cause unpredictable risks such as infinite loops. You can use the for loop when inserting or deleting data.
let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
for(let i = 0; i < 10; i++) {
  lightWeightSet.add(i + "123");
}
for(let i = 0; i < 10; i++) {
  lightWeightSet.remove(i + "123");
}

entries

entries(): IterableIterator<[T, T]>

Obtains an iterator that contains all the elements in this container.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let iter = lightWeightSet.entries();
let index = 0;
while(index < lightWeightSet.length) {
  console.log(JSON.stringify(iter.next().value));
  index++;
}

// You are not advised to use the add, remove, or removeAt APIs in entries because they may cause unpredictable risks such as infinite loops. You can use the for loop when inserting or deleting data.
let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
for(let i = 0; i < 10; i++) {
  lightWeightSet.add(i + "123");
}
for(let i = 0; i < 10; i++) {
  lightWeightSet.remove(i + "123");
}

[Symbol.iterator]

[Symbol.iterator](): IterableIterator&lt;T&gt;

Obtains an iterator, each item of which is a JavaScript object.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");

// Method 1:
let nums: Array<string> = lightWeightSet.toArray()
for (let item of nums) {
  console.log("value:" + item);
}

// Method 2:
let iter = lightWeightSet[Symbol.iterator]();
let temp: IteratorResult<string> = iter.next();
while(!temp.done) {
  console.log("value:" + temp.value);
  temp = iter.next();
}

// You are not advised to use the add, remove, or removeAt APIs in Symbol.iterator because they may cause unpredictable risks such as infinite loops. You can use the for loop when inserting or deleting data.
let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
for(let i = 0; i < 10; i++) {
  lightWeightSet.add(i + "123");
}
for(let i = 0; i < 10; i++) {
  lightWeightSet.remove(i + "123");
}

equal^(deprecated)

equal(obj: Object): boolean

Checks whether the elements of this container are the same as those of obj.

NOTE

This API is supported since API version 10 and deprecated since API version 12. There is no substitute API.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet: LightWeightSet<string> = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let obj = ["sparrow", "squirrel"];
let result = lightWeightSet.equal(obj);

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