In Java, the HashMap class is widely used for storing key-value pairs. It is important to know the size of a HashMap at any given point, as it can help in analyzing and optimizing the performance of your code.

To get the size of a HashMap, you can use the size() method provided by the HashMap class.

Here’s an example of how to use the size() method to get the size of a HashMap:

import java.util.HashMap;

public class Main {
  public static void main(String[] args) {
    HashMap<String, Integer> hashMap = new HashMap<>();
    hashMap.put("A", 1);
    hashMap.put("B", 2);
    hashMap.put("C", 3);

    int size = hashMap.size();
    System.out.println("Size of HashMap: " + size);
  }
}

In this example, we create a HashMap and add three key-value pairs to it. Then, we use the size() method to get the size of the HashMap. Finally, we print the size to the console.

Running the above code will output:

Size of HashMap: 3

The size() method returns an int value representing the number of key-value pairs present in the HashMap.

It is important to note that the size() method has a time complexity of O(1), meaning it takes constant time to retrieve the size, regardless of the number of elements in the HashMap.

By knowing the size of a HashMap, you can make informed decisions about your code and design efficient algorithms that rely on the size of the HashMap.

#java #hashmap