查找key是否包含map中的值并返回布尔值

 ```python

 my_dict = {"key1": "value1", "key2": "value2", "key3": "value3"}

 if "key1" in my_dict:

     print("Key exists in the map")

 else:

     print("Key does not exist in the map")

 ```

 ```java

 import java.util.HashMap;

 public class Main {

     public static void main(String[] args) {

         HashMap<String, String> myMap = new HashMap<>();

         myMap.put("key1", "value1");

         myMap.put("key2", "value2");

         myMap.put("key3", "value3");

         if (myMap.containsKey("key1")) {

             System.out.println("Key exists in the map");

         } else {

             System.out.println("Key does not exist in the map");

         }

     }

 }

 ```

 ```javascript

 let myMap = new Map();

 myMap.set("key1", "value1");

 myMap.set("key2", "value2");

 myMap.set("key3", "value3");

 if (myMap.has("key1")) {

     console.log("Key exists in the map");

 } else {

     console.log("Key does not exist in the map");

 }

 ```