@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 '@ohos.util.LightWeightSet';  

LightWeightSet

Attributes

System capability: SystemCapability.Utils.Lang

constructor

constructor()

A constructor used to create a LightWeightSet instance.

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

let lightWeightSet = new LightWeightSet();

isEmpty

isEmpty(): boolean

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

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

const lightWeightSet = new LightWeightSet();
let result = lightWeightSet.isEmpty();

add

add(obj: T): boolean

Adds an element to this container.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet = new LightWeightSet();
let result = lightWeightSet.add("squirrel");

addAll

addAll(set: LightWeightSet<T>): boolean

Adds all elements in a LightWeightSet instance to this container.

System capability: SystemCapability.Utils.Lang

Parameters

Error codes

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

Example

let lightWeightSet = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
let set = 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.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

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

has

has(key: T): boolean

Checks whether this container has the specified key.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet = new LightWeightSet();
lightWeightSet.add(123);
let result = lightWeightSet.has(123);

equal

equal(obj: Object): boolean

Checks whether this container contains objects of the same type as the specified obj.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

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

increaseCapacityTo

increaseCapacityTo(minimumCapacity: number): void

Increases the capacity of this container.

System capability: SystemCapability.Utils.Lang

Parameters

Error codes

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

Example

let lightWeightSet = new LightWeightSet();
lightWeightSet.increaseCapacityTo(10);

getIndexOf

getIndexOf(key: T): number

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

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet = 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.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet = 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.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let lightWeightSet = 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.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Parameters

let lightWeightSet = 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.

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

let lightWeightSet = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");
lightWeightSet.clear();

toString

toString(): String

Obtains a string that contains all elements in this container.

System capability: SystemCapability.Utils.Lang

Return value

Example

let lightWeightSet = 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.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let lightWeightSet = 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.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let lightWeightSet = 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.

System capability: SystemCapability.Utils.Lang

Parameters

callbackfn

Error codes

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

Example

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

entries

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

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

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let lightWeightSet = 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++;
}

[Symbol.iterator]

[Symbol.iterator](): IterableIterator<T>

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

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let lightWeightSet = new LightWeightSet();
lightWeightSet.add("squirrel");
lightWeightSet.add("sparrow");

// Method 1:
for (let item of lightWeightSet) { 
  console.log("value:" + item);
}

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