@ohos.util.ArrayList (Linear Container ArrayList)

ArrayList is a linear data structure that is implemented based on arrays. ArrayList can dynamically adjust the capacity based on project requirements. It increases the capacity by 50% each time.

Similar to ArrayList, Vector is also implemented based on arrays and can dynamically adjust the capacity. It increases the capability by 100% each time.

When compared with LinkedList, ArrayList is more efficient in random access but less efficient in the addition or removal operation, because its addition or removal operation affects the position of other elements in the container.

Recommended use case: Use ArrayList when elements in a container need to be frequently read.

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 ArrayList from '@ohos.util.ArrayList';

ArrayList

Attributes

System capability: SystemCapability.Utils.Lang

constructor

constructor()

A constructor used to create an ArrayList instance.

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

let arrayList: ArrayList<string | number> = new ArrayList();

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

class C1 {
  name: string = ""
  age: string = ""
}
let arrayList: ArrayList<string | number | boolean | Array<number> | C1> = new ArrayList();
let result1 = arrayList.add("a");
let arrayList1: ArrayList<number> = new ArrayList();
let result2 = arrayList.add(1);
let b = [1, 2, 3];
let result3 = arrayList.add(b);
let c : C1 = {name: "Dylon", age: "13"}
let result4 = arrayList.add(c);
let result5 = arrayList.add(false);

insert

insert(element: T, index: number): 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 arrayList: ArrayList<number | string | boolean> = new ArrayList();
arrayList.insert("A", 0);
arrayList.insert(0, 1);
arrayList.insert(true, 2);

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 arrayList: ArrayList<string> = new ArrayList();
arrayList.add("squirrel");
let result: boolean = arrayList.has("squirrel");

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 arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(2);
arrayList.add(1);
arrayList.add(2);
arrayList.add(4);
let result: number = arrayList.getIndexOf(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 arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(2);
arrayList.add(1);
arrayList.add(2);
arrayList.add(4);
let result: number = arrayList.getLastIndexOf(2);

removeByIndex

removeByIndex(index: number): T

Removes an element with 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 arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(2);
arrayList.add(4);
let result: number = arrayList.removeByIndex(2);

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 arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
let result: boolean = arrayList.remove(2);

removeByRange

removeByRange(fromIndex: number, toIndex: number): void

Removes from this container all of the elements within a range, including the element at the start position but not that at the end position.

System capability: SystemCapability.Utils.Lang

Parameters

Error codes

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

Example

let arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
arrayList.removeByRange(2, 4);

replaceAllElements

replaceAllElements(callbackFn: (value: T, index?: number, arrlist?: ArrayList<T>) => T, thisArg?: Object): void

Replaces all elements in this container with new elements, and returns the new ones.

System capability: SystemCapability.Utils.Lang

Parameters

callbackFn

Error codes

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

Example

let arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
arrayList.replaceAllElements((value: number): number => {
  // Add the user operation logic based on the actual scenario.
  return value;
});

forEach

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

sort

sort(comparator?: (firstValue: T, secondValue: T) => number): void

Sorts elements in this container.

System capability: SystemCapability.Utils.Lang

Parameters

comparator

Error codes

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

Example

let arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
arrayList.sort((a: number, b: number) => a - b);
arrayList.sort((a: number, b: number) => b - a);
arrayList.sort();

subArrayList

subArrayList(fromIndex: number, toIndex: number): ArrayList<T>

Obtains elements within a range in this container, including the element at the start position but not that at the end position, and returns these elements as a new ArrayList instance.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

Error codes

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

Example

let arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
let result: ArrayList<number> = arrayList.subArrayList(2, 4);

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 arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
arrayList.clear();

clone

clone(): ArrayList<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 arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
let result:  ArrayList<number> = arrayList.clone();

getCapacity

getCapacity(): number

Obtains the capacity of this container.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
let result: number = arrayList.getCapacity();

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 arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
let result: Array<number> = arrayList.convertToArray();

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

let arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
let result: boolean = arrayList.isEmpty();

increaseCapacityTo

increaseCapacityTo(newCapacity: 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 arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
arrayList.increaseCapacityTo(2);
arrayList.increaseCapacityTo(8);

trimToCurrentLength

trimToCurrentLength(): void

Trims the capacity of this container to its current length.

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

let arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);
arrayList.trimToCurrentLength();

[Symbol.iterator]

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

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

NOTE

This API cannot be used in .ets files.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let arrayList: ArrayList<number> = new ArrayList();
arrayList.add(2);
arrayList.add(4);
arrayList.add(5);
arrayList.add(4);

// Method 1:
let numbers: Array<number> = arrayList.convertToArray()
for (let item of numbers) {
  console.log(`value : ${item}`);
}

// Method 2:
let iter = arrayList[Symbol.iterator]();
let temp: IteratorResult<number> = iter.next();
while(!temp.done) {
    console.log(`value:${temp.value}`);
    temp = iter.next();
}