Linear Container LinkedList
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.
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 less efficient in data access than ArrayList.
Recommended use case: Use LinkedList for frequent insertion and removal operations.
Modules to Import
import LinkedList from '@ohos.util.LinkedList';
LinkedList
Attributes
System capability: SystemCapability.Utils.Lang
Name | Type | Readable | Writable | Description |
---|---|---|---|---|
length | number | Yes | No | Number of elements in a linked list (called container later). |
constructor
constructor()
A constructor used to create a LinkedList instance.
System capability: SystemCapability.Utils.Lang
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
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the element is added successfully; returns false otherwise. |
Example
let linkedList = new LinkedList();
let result = linkedList.add("a");
let result1 = linkedList.add(1);
let b = [1, 2, 3];
linkedList.add(b);
let c = {name : "lala", age : "13"};
let result3 = linkedList.add(false);
addFirst
addFirst(element: T): void
Adds an element at the top of this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
Example
let linkedList = new LinkedList();
linkedList.addFirst("a");
linkedList.addFirst(1);
let b = [1, 2, 3];
linkedList.addFirst(b);
let c = {name : "lala", age : "13"};
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
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
index | number | Yes | Index of the position where the element is to be inserted. |
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
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the specified element is contained; returns false otherwise. |
Example
let linkedList = new LinkedList();
let result1 = linkedList.has("Ahfbrgrbgnutfodgorrogorg");
linkedList.add("Ahfbrgrbgnutfodgorrogorg");
let result = linkedList.has("Ahfbrgrbgnutfodgorrogorg");
get
get(index: number): T
Obtains an element at the specified position in this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
index | number | Yes | Position index of the target element. |
Return value
Type | Description |
---|---|
T | Element obtained. |
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
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
Return value
Type | Description |
---|---|
number | Returns the position index if obtained; returns -1 otherwise. |
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
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
Return value
Type | Description |
---|---|
number | Returns the position index if obtained; returns -1 otherwise. |
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
Name | Type | Mandatory | Description |
---|---|---|---|
index | number | Yes | Position index of the target element. |
Return value
Type | Description |
---|---|
T | Element removed. |
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
Type | Description |
---|---|
T | Element removed. |
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
Type | Description |
---|---|
T | Element removed. |
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
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the element is removed successfully; returns false otherwise. |
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
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the element is removed successfully; returns false otherwise. |
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
Name | Type | Mandatory | Description |
---|---|---|---|
element | T | Yes | Target element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the element is removed successfully; returns false otherwise. |
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
Type | Description |
---|---|
LinkedList<T> | New LinkedList instance obtained. |
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
Name | Type | Mandatory | Description |
---|---|---|---|
callbackfn | function | Yes | Callback invoked to traverse the elements in the container. |
thisArg | Object | No | Value to use when the callback is invoked. |
callbackfn
Name | Type | Mandatory | Description |
---|---|---|---|
value | T | Yes | Value of the element that is currently traversed. |
index | number | No | Position index of the element that is currently traversed. |
LinkedList | LinkedList<T> | No | Instance that invokes the forEach API. |
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);
});
clear
clear(): void
Clears this container and sets its length to 0.
System capability: SystemCapability.Utils.Lang
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
Name | Type | Mandatory | Description |
---|---|---|---|
index | number | Yes | Position index of the target element. |
element | T | Yes | Element to be used for replacement. |
Return value
Type | Description |
---|---|
T | New element. |
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
Type | Description |
---|---|
Array<T> | Array obtained. |
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
Type | Description |
---|---|
T | Returns the element if obtained; returns undefined otherwise. |
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
Type | Description |
---|---|
T | Returns the element if obtained; returns undefined otherwise. |
Example
let linkedList = new LinkedList();
linkedList.add(2);
linkedList.add(4);
linkedList.add(5);
linkedList.add(4);
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
Type | Description |
---|---|
IterableIterator<T> | Iterator obtained. |
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;
}