Nonlinear Container HashSet
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.
HashSet is implemented based on HashMap. In HashSet, only the value object is processed.
Unlike TreeSet, which stores and accesses data in sorted order, HashSet stores data in a random order. This means that HashSet may use a different order when storing and accessing elements. Both of them allows only unique elements. However, null values are allowed in HashSet, but not allowed in TreeSet.
Recommended use case: Use HashSet when you need a set that has only unique elements or need to deduplicate a set.
This topic uses the following to identify the use of generics:
- T: Type
Modules to Import
import HashSet from '@ohos.util.HashSet';
HashSet
Attributes
System capability: SystemCapability.Utils.Lang
Name | Type | Readable | Writable | Description |
---|---|---|---|---|
length | number | Yes | No | Number of elements in a hash set (called container later). |
Example
let hashSet = new HashSet();
hashSet.add(1);
hashSet.add(2);
hashSet.add(3);
hashSet.add(4);
hashSet.add(5);
let res = hashSet.length;
constructor
constructor()
A constructor used to create a HashSet instance.
System capability: SystemCapability.Utils.Lang
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200012 | The HashSet's constructor cannot be directly invoked. |
Example
let hashSet = new HashSet();
try {
let hashSet2 = HashSet();
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
isEmpty
isEmpty(): boolean
Checks whether this container is empty (contains no element).
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
boolean | Returns true if the container is empty; returns false otherwise. |
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The isEmpty method cannot be bound. |
Example
const hashSet = new HashSet();
let result = hashSet.isEmpty();
try {
hashSet.isEmpty.bind({})(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
has
has(value: T): boolean
Checks whether this container contains the specified element.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
value | T | Yes | Target element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the specified element is contained; returns false otherwise. |
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The has method cannot be bound. |
Example
let hashSet = new HashSet();
let result = hashSet.has("squirrel");
hashSet.add("squirrel");
let result1 = hashSet.has("squirrel");
try {
hashSet.has.bind({}, "squirrel")(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
add
add(value: T): boolean
Adds an element to this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
value | T | Yes | Target element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the element is added successfully; returns false otherwise. |
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The add method cannot be bound. |
Example
let hashSet = new HashSet();
let result = hashSet.add("squirrel");
try {
hashSet.add.bind({}, "squirrel")(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
remove
remove(value: T): boolean
Removes an element from this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
value | T | Yes | Target element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the element is removed successfully; returns false otherwise. |
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The remove method cannot be bound. |
Example
let hashSet = new HashSet();
hashSet.add("squirrel");
hashSet.add("sparrow");
let result = hashSet.remove("sparrow");
try {
hashSet.remove.bind({}, "sparrow")(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
clear
clear(): void
Clears this container and sets its length to 0.
System capability: SystemCapability.Utils.Lang
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The clear method cannot be bound. |
Example
let hashSet = new HashSet();
hashSet.add("squirrel");
hashSet.add("sparrow");
hashSet.clear();
try {
hashSet.remove.bind({})(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
values
values(): IterableIterator<T>
Obtains an iterator that contains all the values in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
IterableIterator<T> | Iterator obtained. |
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The values method cannot be bound. |
Example
let hashSet = new HashSet();
hashSet.add("squirrel");
hashSet.add("sparrow");
let iter = hashSet.values();
let temp = iter.next().value;
while(temp != undefined) {
console.log("value:" + temp);
temp = iter.next().value;
}
try {
hashSet.values.bind({})(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
forEach
forEach(callbackfn: (value?: T, key?: T, set?: HashSet<T>) => void, thisArg?: Object): void
Uses a callback to traverse the elements in this container and obtain their position indexes.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
callbackfn | function | Yes | Callback invoked to traverse the elements in the container. |
thisArg | Object | No | Value to use when the callback is invoked. |
callbackfn
Name | Type | Mandatory | Description |
---|---|---|---|
value | T | No | Value of the element that is currently traversed. |
key | T | No | Key of the element that is currently traversed (same as value). |
set | HashSet<T> | No | Instance that invokes the forEach method. |
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The forEach method cannot be bound. |
Example
let hashSet = new HashSet();
hashSet.add("sparrow");
hashSet.add("squirrel");
hashSet.forEach((value, key) => {
console.log("value:" + value, key);
});
try {
hashSet.forEach.bind({}, (value, key) => {
console.log("value:" + value, key);
})(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
entries
entries(): IterableIterator<[T, T]>
Obtains an iterator that contains all the elements in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
IterableIterator<[T, T]> | Iterator obtained. |
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The entries method cannot be bound. |
Example
let hashSet = new HashSet();
hashSet.add("squirrel");
hashSet.add("sparrow");
let iter = hashSet.entries();
let temp = iter.next().value;
while(temp != undefined) {
console.log("key:" + temp[0]);
console.log("value:" + temp[1]);
temp = iter.next().value;
}
try {
hashSet.entries.bind({})(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}
[Symbol.iterator]
[Symbol.iterator](): IterableIterator<T>
Obtains an iterator, each item of which is a JavaScript object.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
IterableIterator<T> | Iterator obtained. |
Error codes
For details about the error codes, see containers Error Codes.
ID | Error Message |
---|---|
10200011 | The Symbol.iterator method cannot be bound. |
Example
let hashSet = new HashSet();
hashSet.add("squirrel");
hashSet.add("sparrow");
// Method 1:
for (let item of hashSet) {
console.log("value: " + item);
}
// Method 2:
let iter = hashSet[Symbol.iterator]();
let temp = iter.next().value;
while(temp != undefined) {
console.log("value: " + temp);
temp = iter.next().value;
}
try {
hashSet[Symbol.iterator].bind({})(); // bind() creates a new bound function that, when called, has its this keyword set to the provided value. It is used to test exception capture.
} catch(err) {
console.log(`${err.code} - ${err.name} - ${err.message}`);
}