#     
#  Overview

The **`containsKey()` method** in Dart checks if an entry for the specified key is present in **`SplayTreeMap`**.

##   
## Syntax

```dart
bool containsKey(Object? key)
```
**Argument**: This is the `key` to be searched and passed as an argument.

## Return value 
This method returns `true` if there is an entry for the provided `key`. Otherwise, it returns `false`.

## Code
The code below demonstrates how to use `containsKey()` to check if there is an entry present for the specified key:


import 'dart:collection';
void main() {
  //Create a new SplayTreeMap that can have the int key and string values
  SplayTreeMap map = new SplayTreeMap<int, String>((keya,keyb) =>  keyb.compareTo(keya));

  // Add five entries to the map
  map[5] = "Five";
  map[4] = "Four";
  map[2] = "Two";
  map[1] = "One";
  map[3] = "Three";

  print('The map is $map');

  print('map.containsKey(5) : ${map.containsKey(5)}');
  print('map.containsKey(10) : ${map.containsKey(10)}');

}

#    
## Code explanation 

**Line 1**: We import the **`collection`** library. 

**Line 4**: We create a new `SplayTreeMap` object named `map`. We pass a `compare` function as an argument. This function maintains the order of the `map` entries. In our case, the `compare` function orders the elements in descending order.

**Lines 7 to 11**: We add five new entries to the `map`. Now, the map is `_{5=Five,4=Four,3=Three,2=Two,1=One}_`.

**Line 15**: We use the `containsKey()` method to check if the `map` contains an entry for the key `5`. The map has an entry for the key `5`, so the methods returns `true`.

**Line 16**: We use the `containsKey()` method to check if the `map` contains an entry for the key `10`. The map doesn't have an entry for the key `10`, so the method returns `false`.

How to use the containsKey() method in Dart

containsKey() in Dart checks for a key's presence in SplayTreeMap and returns true or false accordingly.