@ohos.util.Stack (Linear Container Stack)

Stack is implemented based on the array data structure. It follows the principle Last Out First In (LOFI) and supports data insertion and removal at one end.

Unlike Queue, which is implemented based on the queue data structure and supports insertion at one end and removal at the other end, Stack supports insertion and removal at the same end.

Recommended use case: Use Stack in LOFI scenarios.

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 Stack from '@ohos.util.Stack';  

Stack

Attributes

System capability: SystemCapability.Utils.Lang

constructor

constructor()

A constructor used to create a Stack instance.

System capability: SystemCapability.Utils.Lang

Error codes

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

Example

let stack : Stack<number | string | Object> = new Stack();

push

push(item: T): T

Adds an element at the top 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 stack : Stack<number | string | C1> = new Stack();
let result = stack.push("a");
let result1 = stack.push(1);
let c : C1  = {name : "Dylon", age : "13"};
let result2 = stack.push(c);

pop

pop(): T

Removes the top 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 stack : Stack<number> = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(2);
stack.push(4);
let result = stack.pop();

peek

peek(): T

Obtains the top element of this container.

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let stack : Stack<number> = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(2);
let result = stack.peek();

locate

locate(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 stack : Stack<number> = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(2);
let result = stack.locate(2);

forEach

forEach(callbackFn: (value: T, index?: number, stack?: Stack<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 stack : Stack<number> = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(4);
stack.forEach((value : number, index ?: number) :void => {
  console.log("value:" + value, "index:" + index);
});

isEmpty

isEmpty(): boolean

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

System capability: SystemCapability.Utils.Lang

Return value

Error codes

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

Example

let stack : Stack<number> = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(4);
let result = stack.isEmpty();

[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 stack : Stack<number> = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(4);

// Method 1:
while(!stack.isEmpty()) {
  // Service logic
  let item = stack.pop()
  console.log("value:" + item);
}

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