# @ohos.util.Vector (Linear Container Vector)

Vector is a linear data structure that is implemented based on arrays. When the memory of a vector is used up, a larger contiguous memory area is automatically allocated, all the elements are copied to the new memory area, and the current memory area is reclaimed. Vector can be used to efficiently access elements.

Both Vector and [ArrayList](js-apis-arraylist.md) are implemented based on arrays, but Vector provides more interfaces for operating the arrays. Both of them can dynamically adjust the capacity. Vector doubles the capacity each time, whereas ArrayList increases the capacity by 50%.

**Recommended use case**: Use Vector when the data volume is large.

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.
>
> The APIs provided by this module are deprecated since API version 9. You are advised to use [@ohos.util.ArrayList](js-apis-arraylist.md).

## Modules to Import

```ts
import { Vector } from '@kit.ArkTS';
```


## Vector

### Properties

**System capability**: SystemCapability.Utils.Lang

| Name| Type| Readable| Writable| Description|
| -------- | -------- | -------- | -------- | -------- |
| length | number | Yes| No| Number of elements in a Vector.|


### constructor

constructor()

A constructor used to create a **Vector** instance.

**System capability**: SystemCapability.Utils.Lang

**Example**

```ts
let vector : Vector<string | number | Array<number>> = new Vector();
```


### add

add(element: T): boolean

Adds an element at the end of this Vector.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Target element.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Operation result. The value **true** is returned if the element is added; otherwise, **false** is returned.|

**Example**

```ts
class C1 {
  name: string = ""
  age: string = ""
}
let vector : Vector<string | number | C1 | Array<number>> = new Vector();
let result = vector.add("a");
let result1 = vector.add(1);
let b = [1, 2, 3];
let result2 = vector.add(b);
let c: C1 = {name : "Jack", age : "13"};
let result3 = vector.add(c);
```

### insert

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

Inserts an element within the length range and moves its subsequent elements rightwards.

**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**

```ts
let vector : Vector<string | number | Object | Array<number>> = new Vector();
vector.insert("A", 0);
vector.insert(0, 1);
vector.insert(true, 2);
```

### has

has(element: T): boolean

Checks whether this Vector has the specified element.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Target element.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Check result. The value **true** is returned if the Vector has the specified element; otherwise, **false** is returned.|

**Example**

```ts
let vector : Vector<string> = new Vector();
let result = vector.has("squirrel");
vector.add("squirrel");
let result1 = vector.has("squirrel");
```

### getIndexOf

getIndexOf(element: T): number

Obtains the index of the first occurrence of the specified element in this Vector.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Target element.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Index of the element. If no match is found, **-1** is returned.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(2);
vector.add(1);
vector.add(2);
vector.add(4);
let result = vector.getIndexOf(2);
```

### getLastIndexOf

getLastIndexOf(element: T): number

Obtains the index of the last occurrence of the specified element in this Vector.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Target element.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Index of the element. If no match is found, **-1** is returned.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(2);
vector.add(1);
vector.add(2);
vector.add(4);
let result = vector.getLastIndexOf(2);
```

### removeByIndex

removeByIndex(index: number): T

Searches for an element based on its index, removes the element after returning it, and moves its subsequent elements leftwards.

**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. If the Vector is empty, **undefined** is returned. If the index is out of range, an exception is thrown.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(2);
vector.add(4);
let result = vector.removeByIndex(2);
```

### remove

remove(element: T): boolean

Removes the first occurrence of the specified element from this Vector.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Target element.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Operation result. The value **true** is returned if the element is removed; otherwise, **false** is returned.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.remove(2);
```

### removeByRange

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

Removes from this Vector 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.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.removeByRange(2,4);
```

### replaceAllElements

replaceAllElements(callbackFn: (value: T, index?: number, vector?: Vector&lt;T&gt;) => T,
thisArg?: Object): void

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

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| callbackFn | function | Yes| Callback invoked for 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**.|
| vector | Vector&lt;T&gt; | No| Instance that calls the **replaceAllElements** API. The default value is this instance.|

**Example**

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

### forEach

forEach(callbackFn: (value: T, index?: number, vector?: Vector&lt;T&gt;) => void,
thisArg?: Object): void

Uses a callback to traverse the elements in this Vector and obtain their position indexes.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| callbackFn | function | Yes| Callback invoked for 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**.|
| vector | Vector&lt;T&gt; | No| Instance that calls the **forEach** API. The default value is this instance.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.forEach((value : number, index ?: number) : void => {
  console.log("value:" + value, "index:" + index);
});
```

### sort

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

Sorts elements in this Vector.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| comparator | function | No| Callback invoked for sorting. The default value is this instance.|

comparator

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

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.sort((a: number, b: number) => a - b);
vector.sort((a: number, b: number) => b - a);
vector.sort();
```

### subVector

subVector(fromIndex: number, toIndex: number): Vector&lt;T&gt;

Obtains elements within a range in this Vector, including the element at the start position but not that at the end position, and returns these elements as a new **Vector** 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|
| -------- | -------- |
| Vector&lt;T&gt; | New **Vector** instance obtained.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.add(6);
vector.add(8);
let result = vector.subVector(0,4);
let result1 = vector.subVector(2,4);

```

### clear

clear(): void

Clears all elements in this Vector and sets its length to **0**.

**System capability**: SystemCapability.Utils.Lang

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.clear();
```

### clone

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

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

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| Vector&lt;T&gt; | New **Vector** instance obtained.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.clone();
```

### getCapacity

getCapacity(): number

Obtains the capacity of this Vector.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Capacity obtained.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.getCapacity();
```

### convertToArray

convertToArray(): Array&lt;T&gt;

Converts this Vector into an array.

**System capability**: SystemCapability.Utils.Lang

**Return value**

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

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.convertToArray();
```

### isEmpty

isEmpty(): boolean

Checks whether this Vector is empty (contains no elements).

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Check result. The value **true** is returned if the Vector is empty; otherwise, **false** is returned.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.isEmpty();
```

### increaseCapacityTo

increaseCapacityTo(newCapacity: number): void

Increases the capacity of this Vector.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| newCapacity | number | Yes| New capacity.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.increaseCapacityTo(2);
vector.increaseCapacityTo(12);
```

### trimToCurrentLength

trimToCurrentLength(): void

Trims the capacity of this Vector into its current length.

**System capability**: SystemCapability.Utils.Lang

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.trimToCurrentLength();
```

### toString

toString(): string

Uses commas (,) to concatenate elements in this Vector into a string.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| string | String obtained.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.toString();
```

### copyToArray

copyToArray(array: Array&lt;T&gt;): void

Copies elements in this Vector into an array to overwrite elements of the same position indexes.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| array | Array&lt;T&gt; | Yes| Array to which the elements in the Vector will be copied.|

### getFirstElement

getFirstElement(): T

Obtains the first element in this Vector.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| T | The first element obtained.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.getFirstElement();
```

### getLastElement

getLastElement(): T

Obtains the last element in this Vector.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| T | The last element obtained.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.getLastElement();
```

### getLastIndexFrom

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

Searches for an element backward from the specified position index and returns the position index of the element.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Target element.|
| index | number | Yes| Position index where the search starts.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Index of the element. If no match is found, **-1** is returned.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.getLastIndexFrom(4,3);
```

### getIndexFrom

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

Searches for an element forward from the specified position index and returns the position index of the element.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Target element.|
| index | number | Yes| Position index where the search starts.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Index of the element. If no match is found, **-1** is returned.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.getIndexFrom(4, 3);
```

### setLength

setLength(newSize: number): void

Sets a new length for this Vector.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| newSize | number | Yes| New length to set.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.setLength(8);
vector.setLength(2);
```

### get

get(index: number): T 

Obtains an element at the specified position in this Vector.

**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**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.get(2);
```

### set

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

Replaces an element at the specified position in this Vector 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.|

### [Symbol.iterator]

[Symbol.iterator]\(): IterableIterator&lt;T&gt;

Returns 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.|

**Example**

```ts
let vector : Vector<number> = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
// Method 1:
let nums: Array<number> =  vector.convertToArray()
for (let item of nums) {
  console.log("value:" + item);
}

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