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.
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. |
Example
let treeSet = 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. |
Example
const treeSet = 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. |
Example
let treeSet = new TreeSet();
treeSet.has(123);
treeSet.add(123);
let result1 = 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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
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. |
Example
let treeSet = new TreeSet();
let result = treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
let result = treeSet.remove("sdfs");
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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
treeSet.add("zdfgsd");
let result = treeSet.getLowerValue("sdfs");
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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
treeSet.add("zdfgsd");
let result = treeSet.getHigherValue("sdfs");
popFirst
popFirst(): T
Removes the first element in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
T | Element removed. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
let result = treeSet.popLast();
clear
clear(): void
Clears this container and sets its length to 0.
System capability: SystemCapability.Utils.Lang
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
let iter = treeSet.values();
let temp = iter.next().value;
while(temp != undefined) {
console.log("value:" + temp);
temp = iter.next().value;
}
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 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 | TreeSet<T> | No | Instance that invokes the forEach method. |
Example
let treeSet = new TreeSet();
treeSet.add("sdfs");
treeSet.add("dfsghsf");
treeSet.forEach((value, key) => {
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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
let iter = treeSet.entries();
let temp = iter.next().value;
while(temp != undefined) {
console.log("key:" + temp[0]);
console.log("value:" + temp[1]);
temp = iter.next().value;
}
[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. |
Example
let treeSet = new TreeSet();
treeSet.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeSet.add("sdfs");
// Method 1:
for (let item of treeSet) {
console.log("value:" + item);
}
// Method 2:
let iter = treeSet[Symbol.iterator]();
let temp = iter.next().value;
while(temp != undefined) {
console.log("value:" + temp);
temp = iter.next().value;
}