@ohos.util.LinkedList (Linear Container LinkedList)

LinkedList is implemented based on the doubly linked list. Each node of the doubly linked list has references pointing to the previous element and the next element. When querying an element, the system traverses the list from the beginning or end. LinkedList offers efficient insertion and removal operations but supports low query efficiency. LinkedList allows null elements.

Unlike List, which is a singly linked list, LinkedList is a doubly linked list that supports insertion and removal at both ends.

LinkedList is more efficient in data insertion than ArrayList, but less efficient in data access.

Recommended use case: Use LinkedList for frequent insertion and removal operations.

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 LinkedList from '@ohos.util.LinkedList';  

LinkedList

Attributes

System capability: SystemCapability.Utils.Lang

constructor

constructor()

A constructor used to create a LinkedList instance.

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

let linkedList = new LinkedList();

add

add(element: T): boolean

Adds an element at the end of this container.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let linkedList = new LinkedList();
let result = linkedList.add("a");
let result1 = linkedList.add(1);
let b = [1, 2, 3];
let result2 = linkedList.add(b);
let c = {name : "Dylon", age : "13"};
let result3 = linkedList.add(c);
let result4 = linkedList.add(false);

addFirst

addFirst(element: T): void

Adds an element at the top of this container.

System capability: SystemCapability.Utils.Lang

Parameters

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.addFirst("a");
linkedList.addFirst(1);
let b = [1, 2, 3];
linkedList.addFirst(b);
let c = {name : "Dylon", age : "13"};
linkedList.addFirst(c);
linkedList.addFirst(false);

insert

insert(index: number, element: T): void

Inserts an element at the specified position in this container.

System capability: SystemCapability.Utils.Lang

Parameters

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.insert(0, "A");
linkedList.insert(1, 0);
linkedList.insert(2, true);

has

has(element: T): boolean

Checks whether this container has the specified element.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.add("squirrel");
let result = linkedList.has("squirrel");

get

get(index: number): T

Obtains an 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.

Example

let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(2);
linkedList.add(1);
linkedList.add(2);
linkedList.add(4);
let result = linkedList.get(2);

getLastIndexOf

getLastIndexOf(element: T): number

Obtains the index of the last occurrence of the specified element 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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(2);
linkedList.add(1);
linkedList.add(2);
linkedList.add(4);
let result = linkedList.getLastIndexOf(2);

getIndexOf

getIndexOf(element: T): number

Obtains the index of the first occurrence of the specified element 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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(2);
linkedList.add(1);
linkedList.add(2);
linkedList.add(4);
let result = linkedList.getIndexOf(2);

removeByIndex

removeByIndex(index: number): T

Removes an 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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(2);
linkedList.add(4);
let result = linkedList.removeByIndex(2);

removeFirst

removeFirst(): T

Removes the first element from this container.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(2);
linkedList.add(4);
let result = linkedList.removeFirst();

removeLast

removeLast(): T

Removes the last element from this container.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(2);
linkedList.add(4);
let result = linkedList.removeLast();

remove

remove(element: T): boolean

Removes the first occurrence of the specified element 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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
let result = linkedList.remove(2);

removeFirstFound

removeFirstFound(element: T): boolean

Removes the first occurrence of the specified element 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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
let result = linkedList.removeFirstFound(4);

removeLastFound

removeLastFound(element: T): boolean

Removes the last occurrence of the specified element 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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
let result = linkedList.removeLastFound(4);

clone

clone(): LinkedList<T>

Clones this container and returns a copy. The modification to the copy does not affect the original instance.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
let result = linkedList.clone();

forEach

forEach(callbackFn: (value: T, index?: number, LinkedList?: LinkedList<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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
linkedList.forEach((value, index) => {
    console.log("value:" + value, "index:" + index);
});

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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
linkedList.clear();

set

set(index: number, element: T): T

Replaces an element at the specified position in this container with a given element.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
let result = linkedList.set(2, "b");

convertToArray

convertToArray(): Array<T>

Converts this container into an array.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
let result = linkedList.convertToArray();

getFirst

getFirst(): T

Obtains the first element in this container.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
let result = linkedList.getFirst();

getLast

getLast(): T

Obtains the last element in this container.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
let result = linkedList.getLast();

[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 linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);

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

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