@ohos.util.TreeMap (Nonlinear Container TreeMap)
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.
This topic uses the following to identify the use of generics:
-
K: Key
-
V: Value
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 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. It supports sorting elements in ascending or descending order by using comparators.
System capability: SystemCapability.Utils.Lang
Parameters
Name | Type | Mandatory | Description |
---|---|---|---|
comparator | function | No | Custom comparator, which can be used to sort elements based on the comparison relationship. 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 TreeMap's constructor cannot be directly invoked. |
Example
// Constructor.
let treeMap : TreeMap<number, number> = new TreeMap();
// Use the comparator firstValue < secondValue if the elements are expected to be sorted in ascending order. Use firstValue > secondValue if the elements are expected to be sorted in descending order.
let treeMap : TreeMap<string,string> = new TreeMap<string,string>((firstValue: string, secondValue: string) : boolean => {return firstValue > secondValue});
treeMap.set("aa","3");
treeMap.set("dd","1");
treeMap.set("cc","2");
treeMap.set("bb","4");
let numbers = Array.from(treeMap.keys())
for (let item of numbers) {
console.log("treeMap:" + item);
}
// When a custom type is inserted, a comparator must be provided.
class TestEntry{
public id: number = 0;
}
let ts1: TreeMap<TestEntry, string> = new TreeMap<TestEntry, string>((t1: TestEntry, t2: TestEntry): boolean => {return t1.id < t2.id;});
let entry1: TestEntry = {
id: 0
};
let entry2: TestEntry = {
id: 1
}
ts1.set(entry1, "0");
ts1.set(entry2, "1");
console.log("treeMap: ", ts1.length);
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
let treeMap : TreeMap<number, number> = 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. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The hasKey method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
let result = treeMap.hasKey("squirrel");
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. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The hasValue method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
let result = 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 obtained. If nothing is obtained, undefined is returned. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The get method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
let result = treeMap.get("sparrow");
getFirstKey
getFirstKey(): K
Obtains the first key in this container.
System capability: SystemCapability.Utils.Lang
Return value
Type | Description |
---|---|
K | Key obtained. If nothing is obtained, undefined is returned. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The getFirstKey method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 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. If nothing is obtained, undefined is returned. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The getLastKey method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 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 object to be added to the container. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The setAll method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
let map : TreeMap<string, number> = new TreeMap();
map.set("demo", 12);
map.setAll(treeMap); // Add all elements in the treeMap to the map.
map.forEach((value ?: number, key ?: string) : void => {
console.log("value" + value, "key" + key); // Print result: 12 demo, 356 sparrow, and 123 squirrel
})
set
set(key: K, value: V): Object
Adds or updates an element in 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. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The set method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 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. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The remove method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
let result = treeMap.remove("sparrow");
getLowerKey
getLowerKey(key: K): K
Obtains the key that is equal to 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. If nothing is obtained, undefined is returned. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The getLowerKey method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
treeMap.set("gander", 356);
let result = treeMap.getLowerKey("sparrow");
getHigherKey
getHigherKey(key: K): K
Obtains the key that is equal to or 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. If nothing is obtained, undefined is returned. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The getHigherKey method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
treeMap.set("gander", 356);
let result = treeMap.getHigherKey("sparrow");
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. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The replace method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("sparrow", 123);
let result = treeMap.replace("sparrow", 357);
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 treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 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. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The keys method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
let it = treeMap.keys();
let t: IteratorResult<string> = it.next();
while(!t.done) {
console.log("TreeMap " + t.value);
t = it.next()
}
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. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The values method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
let it = treeMap.values();
let t: IteratorResult<number> = it.next();
while(!t.done) {
console.log("TreeMap" + t.value);
t = it.next()
}
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 of this to use when callbackFn is invoked. The default value is this instance. |
callbackFn
Name | Type | Mandatory | Description |
---|---|---|---|
value | V | No | Value of the element that is currently traversed. The default value is the value of the first key-value pair. |
key | K | No | Key of the element that is currently traversed. The default value is the key of the first key-value pair. |
map | TreeMap<K, V> | 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 treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("sparrow", 123);
treeMap.set("gull", 357);
treeMap.forEach((value ?: number, key ?: string) : void => {
console.log("value:" + value, "key:" + 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. |
Error codes
For details about the error codes, see Utils Error Codes.
ID | Error Message |
---|---|
10200011 | The entries method cannot be bound. |
Example
let treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
let it = treeMap.entries();
let t: IteratorResult<Object[]> = it.next();
while(!t.done) {
console.log("TreeMap" + t.value);
t = it.next()
}
[Symbol.iterator]
[Symbol.iterator](): IterableIterator<[K, V]>
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
Type | Description |
---|---|
IterableIterator<[K, V]> | 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 treeMap : TreeMap<string, number> = new TreeMap();
treeMap.set("squirrel", 123);
treeMap.set("sparrow", 356);
// Method 1:
let it = treeMap.entries();
let t: IteratorResult<Object[]> = it.next();
while(!t.done) {
console.log("TreeMap" + t.value);
t = it.next()
}
// Method 2:
let iter = treeMap[Symbol.iterator]();
let temp: IteratorResult<Object[]> = iter.next();
while(!temp.done) {
console.log("key:" + temp.value[0]);
console.log("value:" + temp.value[1]);
temp = iter.next();
}