Java 集合 检查HashMap中是否存在特定键

import java.util.HashMap;

public class CheckKeyExample {

 public static void main(String[] args) {

    // Creating a HashMap of int keys and String values
    HashMap<Integer, String> hashmap = new HashMap<Integer, String>();

    // Adding Key and Value pairs to HashMap
    hashmap.put(11,"Chaitanya");
    hashmap.put(22,"Pratap");
    hashmap.put(33,"Singh");
    hashmap.put(44,"Rajesh");
    hashmap.put(55,"Kate");

    // Checking Key Existence
    boolean flag = hashmap.containsKey(22);
    System.out.println("Key 22 exists in HashMap? : " + flag);

    boolean flag2 = hashmap.containsKey(55);
    System.out.println("Key 55 exists in HashMap? : " + flag2);

    boolean flag3 = hashmap.containsKey(99);
    System.out.println("Key 99 exists in HashMap? : " + flag3);
 }
}

Key 22 exists in HashMap? : true
Key 55 exists in HashMap? : true
Key 99 exists in HashMap? : false