harmony 鸿蒙@ohos.util.ArrayList (Linear Container ArrayList)

  • 2022-08-09
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@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

Name Type Readable Writable Description
length number Yes No Number of elements in an array list (called container later).

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.

ID Error Message
10200012 The ArrayList’s constructor cannot be directly invoked.

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

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.

Error codes

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

ID Error Message
10200011 The add method cannot be bound.

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

Name Type Mandatory Description
element T Yes Target element.
index number Yes Index of the position where the element is to be inserted.

Error codes

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

ID Error Message
10200011 The insert method cannot be bound.
10200001 The value of index is out of range.

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

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.

Error codes

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

ID Error Message
10200011 The has method cannot be bound.

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

Name Type Mandatory Description
element T Yes Target element.

Return value

Type Description
number Returns the position index if obtained; returns -1 if the specified element is not found.

Error codes

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

ID Error Message
10200011 The getIndexOf method cannot be bound.

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

Name Type Mandatory Description
element T Yes Target element.

Return value

Type Description
number Returns the position index if obtained; returns -1 if the specified element is not found.

Error codes

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

ID Error Message
10200011 The getLastIndexOf method cannot be bound.

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

Name Type Mandatory Description
index number Yes Position index of the target element.

Return value

Type Description
T Element removed.

Error codes

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

ID Error Message
10200011 The removeByIndex method cannot be bound.
10200001 The value of index is out of range.

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

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.

Error codes

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

ID Error Message
10200011 The remove method cannot be bound.

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

Name Type Mandatory Description
fromIndex number Yes Index of the start position.
toIndex number Yes Index of the end position.

Error codes

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

ID Error Message
10200011 The removeByRange method cannot be bound.
10200001 The value of fromIndex or toIndex is out of range.

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&lt;T&gt;) => T, thisArg?: Object): void

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

System capability: SystemCapability.Utils.Lang

Parameters

Name Type Mandatory Description
callbackFn function Yes Callback invoked for the replacement.
thisArg Object No Value of this to use when callbackFn is invoked. The default value is this instance.

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. The default value is 0.
arrlist ArrayList&lt;T&gt; No Instance that calls the replaceAllElements API. The default value is this instance.

Error codes

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

ID Error Message
10200011 The replaceAllElements method cannot be bound.

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&lt;T&gt;) => 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 for the replacement.
thisArg Object No Value of this to use when callbackFn is invoked. The default value is this instance.

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. The default value is 0.
arrlist ArrayList&lt;T&gt; No Instance that calls the forEach API. The default value is this instance.

Error codes

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

ID Error Message
10200011 The forEach method cannot be bound.

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

Name Type Mandatory Description
comparator function No Callback invoked for sorting. The default value is the callback function for sorting elements in ascending order.

comparator

Name Type Mandatory Description
firstValue T Yes Previous element.
secondValue T Yes Next element.

Error codes

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

ID Error Message
10200011 The sort method cannot be bound.

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&lt;T&gt;

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

Name Type Mandatory Description
fromIndex number Yes Index of the start position.
toIndex number Yes Index of the end position.

Return value

Type Description
ArrayList&lt;T&gt; New ArrayList instance obtained.

Error codes

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

ID Error Message
10200011 The subArrayList method cannot be bound.
10200001 The value of fromIndex or toIndex is out of range.

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.

ID Error Message
10200011 The clear method cannot be bound.

Example

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

clone

clone(): ArrayList&lt;T&gt;

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
ArrayList&lt;T&gt; New ArrayList instance obtained.

Error codes

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

ID Error Message
10200011 The clone method cannot be bound.

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

Type Description
number Capacity obtained.

Error codes

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

ID Error Message
10200011 The getCapacity method cannot be bound.

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&lt;T&gt;

Converts this container into an array.

System capability: SystemCapability.Utils.Lang

Return value

Type Description
Array&lt;T&gt; Array obtained.

Error codes

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

ID Error Message
10200011 The convertToArray method cannot be bound.

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

Type Description
boolean Returns true if the container is empty; returns false otherwise.

Error codes

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

ID Error Message
10200011 The isEmpty method cannot be bound.

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

Name Type Mandatory Description
newCapacity number Yes New capacity.

Error codes

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

ID Error Message
10200011 The increaseCapacityTo method cannot be bound.

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.

ID Error Message
10200011 The trimToCurrentLength method cannot be bound.

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&lt;T&gt;

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

System capability: SystemCapability.Utils.Lang

Return value

Type Description
IterableIterator&lt;T&gt; Iterator obtained.

Error codes

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

ID Error Message
10200011 The Symbol.iterator method cannot be bound.

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().value;
while(!temp.done) {
    console.log(`value:${temp.value}`);
    temp = iter.next();
}

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