harmony 鸿蒙@ohos.util.TreeSet (Nonlinear Container TreeSet)
@ohos.util.TreeSet (Nonlinear Container TreeSet)
TreeSet is implemented based on TreeMap. In TreeSet, only value objects are processed. TreeSet can be used to store values, each of which must be unique.
HashSet stores data in a random order, whereas TreeSet stores data in sorted order. Both of them allows only unique elements. However, null values are allowed in HashSet, but not allowed in TreeSet.
Recommended use case: Use TreeSet when you need to store data in sorted order.
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 TreeSet from '@ohos.util.TreeSet';
TreeSet
Attributes
System capability: SystemCapability.Utils.Lang
Name | Type | Readable | Writable | Description |
---|---|---|---|---|
length | number | Yes | No | Number of elements in a tree set (called container later). |
constructor
constructor(comparator?: (firstValue: T, secondValue: T) => boolean)
A constructor used to create a TreeSet instance.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
comparator | function | No | Custom comparator. The default value is hole (a blank placeholder), indicating that no comparator. is provided. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200012 | The TreeSet’s constructor cannot be directly invoked. |
Example
let treeSet : TreeSet<string|number|boolean|Object> = new TreeSet();
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
const treeSet : TreeSet<string|number|boolean|Object> = new TreeSet();
let result = treeSet.isEmpty();
has
has(value: T): boolean
Checks whether this container has the specified value.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
value | T | Yes | Target value. |
Return value
Type | Description |
---|---|
boolean | Returns true if the specified value 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 treeSet : TreeSet<number> = new TreeSet();
treeSet.add(123);
let result = treeSet.has(123);
getFirstValue
getFirstValue(): T
Obtains the value of the first element in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
T | Value obtained. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The getFirstValue method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
let result = treeSet.getFirstValue();
getLastValue
getLastValue(): T
Obtains the value of the last element in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
T | Value obtained. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The getLastValue method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
let result = treeSet.getLastValue();
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 Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The add method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
let result = treeSet.add("squirrel");
remove
remove(value: T): boolean
Removes the element with the specified key from this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
value | T | Yes | Key of the 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 treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
let result = treeSet.remove("sparrow");
getLowerValue
getLowerValue(key: T): T
Obtains the value that is placed in front of the input key in this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | T | Yes | Input key. |
Return value
Type | Description |
---|---|
T | Value obtained. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The getLowerValue method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
treeSet.add("gander");
let result = treeSet.getLowerValue("sparrow");
getHigherValue
getHigherValue(key: T): T
Obtains the value that is placed next to the input key in this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | T | Yes | Input key. |
Return value
Type | Description |
---|---|
T | Value obtained. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The getHigherValue method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
treeSet.add("gander");
let result = treeSet.getHigherValue("sparrow");
popFirst
popFirst(): T
Removes the first element in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
T | Element removed. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The popFirst method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
let result = treeSet.popFirst();
popLast
popLast(): T
Removes the last element in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
T | Element removed. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The popLast method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
let result = treeSet.popLast();
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 treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
treeSet.clear();
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 Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The values method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
let it = treeSet.values();
let t: IteratorResult<string> = it.next();
while(!t.done) {
console.log("TreeSet: " + t.value);
t = it.next()
}
forEach
forEach(callbackFn: (value?: T, key?: T, set?: TreeSet<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 of this to use when callbackFn is invoked. The default value is this instance. |
callbackFn |Name|Type|Mandatory|Description| |——–|——–|——–|——–| |value|T|No|Value of the element that is currently traversed. The default value is the value of the first key-value pair.| |key|T|No|Key of the element that is currently traversed. The default value is the key of the first key-value pair.| |set|TreeSet<T>|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 treeSet : TreeSet<string> = new TreeSet();
treeSet.add("sparrow");
treeSet.add("gull");
treeSet.forEach((value ?: string, key ?: string) :void => {
console.log("value:" + value, "key:" + key);
});
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 Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The entries method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
let it = treeSet.entries();
let t: IteratorResult<Object[]> = it.next();
while(!t.done) {
console.log("TreeSet: " + t.value);
t = it.next()
}
[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 Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The Symbol.iterator method cannot be bound. |
Example
let treeSet : TreeSet<string> = new TreeSet();
treeSet.add("squirrel");
treeSet.add("sparrow");
let numbers = Array.from(treeSet.values())
// Method 1:
for (let item of numbers) {
console.log("value:" + item);
}
// Method 2:
let iter = treeSet[Symbol.iterator]();
let temp: IteratorResult<string> = iter.next().value;
while(temp != undefined) {
console.log("value:" + temp);
temp = iter.next().value;
}
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