How do I use a HashMap in Java?

How do I use a HashMap in Java?

A HashMap in Java is a part of the Java Collections Framework. It stores key-value pairs and allows for fast retrieval.

Can you show me a simple example of how to create and use a HashMap?

Sure! Here's a basic example:

import java.util.HashMap;

public class Main {
    public static void main(String[] args) {
        HashMap<String, Integer> map = new HashMap<>();
        map.put("Apple", 1);
        map.put("Banana", 2);
        System.out.println(map.get("Apple")); // Output: 1
    }
}

What are some common methods used with HashMap?

Common methods include put(), get(), remove(), and containsKey(). Each serves a different purpose for managing entries.

Are there any performance considerations I should be aware of?

Yes, HashMaps have average O(1) time complexity for get and put operations, but performance can degrade if many collisions occur.