Nonlinear Container TreeMap
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.
TreeMap stores key-value (KV) pairs. Each key must be unique and have only one value.
TreeMap is implemented using a red-black tree, which is a binary search tree where keys are stored in sorted order for efficient insertion and removal.
HashMap is faster in accessing data than TreeMap, because the former accesses data based on the hash code of the key, whereas the latter stores and accesses the keys in sorted order.
Recommended use case: Use TreeMap when you need to store KV pairs in sorted order.
Modules to Import
import TreeMap from '@ohos.util.TreeMap';
TreeMap
Attributes
System capability: SystemCapability.Utils.Lang
Name | Type | Readable | Writable | Description |
---|---|---|---|---|
length | number | Yes | No | Number of elements in a tree map (called container later). |
constructor
constructor(comparator?:(firstValue: K, secondValue: K) => boolean)
A constructor used to create a TreeMap instance.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
comparator | function | No | Custom comparator. |
Example
let treeMap = new TreeMap();
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 treeMap = new TreeMap();
let result = treeMap.isEmpty();
hasKey
hasKey(key: K): boolean
Checks whether this container has the specified key.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | K | Yes | Target key. |
Return value
Type | Description |
---|---|
boolean | Returns true if the specified key is contained; returns false otherwise. |
Example
let treeMap = new TreeMap();
let result = treeMap.hasKey("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
let result1 = treeMap.hasKey("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
hasValue
hasValue(value: V): boolean
Checks whether this container has the specified value.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
value | V | Yes | Target value. |
Return value
Type | Description |
---|---|
boolean | Returns true if the specified value is contained; returns false otherwise. |
Example
let treeMap = new TreeMap();
let result = treeMap.hasValue(123);
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
let result1 = treeMap.hasValue(123);
get
get(key: K): V
Obtains the value of the specified key in this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | K | Yes | Target key. |
Return value
Type | Description |
---|---|
V | Value of the key. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
let result = treeMap.get("sdfs");
getFirstKey
getFirstKey(): K
Obtains the first key in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
K | Key obtained. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
let result = treeMap.getFirstKey();
getLastKey
getLastKey(): K
Obtains the last key in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
K | Key obtained. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
let result = treeMap.getLastKey();
setAll
setAll(map: TreeMap<K, V>): void
Adds all elements in a TreeMap instance to this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
map | TreeMap<K, V> | Yes | TreeMap instance whose elements are to be added to the current container. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
let map = new TreeMap();
treeMap.setAll(map);
set
set(key: K, value: V): Object
Adds an element to this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | K | Yes | Key of the target element. |
value | V | Yes | Value of the target element. |
Return value
Type | Description |
---|---|
Object | Container that contains the new element. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
remove
remove(key: K): V
Removes the element with the specified key from this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | K | Yes | Target key. |
Return value
Type | Description |
---|---|
V | Value of the element removed. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
treeMap.remove("sdfs");
getLowerKey
getLowerKey(key: K): K
Obtains the key that is placed in front of the input key in this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | K | Yes | Input key. |
Return value
Type | Description |
---|---|
K | Key obtained. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
treeMap.set("zdfgsd", 356);
let result = treeMap.getLowerKey("sdfs");
getHigherKey
getHigherKey(key: K): K
Obtains the key that is placed next to the input key in this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | K | Yes | Input key. |
Return value
Type | Description |
---|---|
K | Key obtained. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
treeMap.set("zdfgsd", 356);
let result = treeMap.getHigherKey("sdfs");
replace
replace(key: K, newValue: V): boolean
Replaces an element in this container.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
key | K | Yes | Key of the target element. |
newValue | V | Yes | New value of the element. |
Return value
Type | Description |
---|---|
boolean | Returns true if the element is replaced successfully; returns false otherwise. |
Example
let treeMap = new TreeMap();
treeMap.set("sdfs", 123);
let result = treeMap.replace("sdfs", 357);
clear
clear(): void
Clears this container and sets its length to 0.
System capability: SystemCapability.Utils.Lang
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
treeMap.clear();
keys
keys(): IterableIterator<K>
Obtains an iterator that contains all the keys in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
IterableIterator<K> | Iterator obtained. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
let iter = treeMap.keys();
let temp = iter.next().value;
while(temp != undefined) {
console.log("value:" + temp);
temp = iter.next().value;
}
values
values(): IterableIterator<V>
Obtains an iterator that contains all the values in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
IterableIterator<V> | Iterator obtained. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
let iter = treeMap.values();
let temp = iter.next().value;
while(temp != undefined) {
console.log("value:" + temp);
temp = iter.next().value;
}
forEach
forEach(callbackfn: (value?: V, key?: K, map?: TreeMap<K, V>) => 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 | V | No | Value of the element that is currently traversed. |
key | K | No | Key of the element that is currently traversed. |
map | TreeMap<K, V> | No | Instance that invokes the forEach method. |
Example
let treeMap = new TreeMap();
treeMap.set("sdfs", 123);
treeMap.set("dfsghsf", 357);
treeMap.forEach((value, key) => {
console.log("value:" + value, key);
});
entries
entries(): IterableIterator<[K, V]>
Obtains an iterator that contains all the elements in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
IterableIterator<[K, V]> | Iterator obtained. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
let iter = treeMap.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<[K, V]>
Obtains an iterator, each item of which is a JavaScript object.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
IterableIterator<[K, V]> | Iterator obtained. |
Example
let treeMap = new TreeMap();
treeMap.set("Ahfbrgrbgnutfodgorrogorgrogofdfdf", 123);
treeMap.set("sdfs", 356);
// Method 1:
for (let item of treeMap) {
console.log("key:" + item[0]);
console.log("value:" + item[1]);
}
// Method 2:
let iter = treeMap[Symbol.iterator]();
let temp = iter.next().value;
while(temp != undefined) {
console.log("key:" + temp[0]);
console.log("value:" + temp[1]);
temp = iter.next().value;
}