LinkedHashMap in Java

Java provides a variety of data structures to store and manipulate collections of objects. One of the useful classes in the Java Collections Framework is `LinkedHashMap`, which is an extension of the `HashMap` class. Unlike `HashMap`, `LinkedHashMap` maintains the order of its elements based on the insertion order, making it useful in scenarios where you need to maintain the order of elements based on their arrival time.

Key Features:

• Stores key-value pairs.
• Implements the Map interface.
• Allows null values and one null key.
• Maintains insertion order.
• Slower than `HashMap` due to maintaining the order.

Usage:

To use `LinkedHashMap`, you need to import the `java.util` package, which contains the Java Collections Framework classes. Here's a basic example of using `LinkedHashMap`:

    import java.util.LinkedHashMap;
    import java.util.Map;

    public class LinkedHashMapExample {
      public static void main(String[] args) {
             // Create a new LinkedHashMap instance
        Map<String, Integer> linkedHashMap = new LinkedHashMap<>();

        // Insert elements into the map
        linkedHashMap.put("kiwi", 10);
        linkedHashMap.put("guava", 5);
        linkedHashMap.put("litchi", 8);

        // Print the elements of the LinkedHashMap
        for (Map.Entry<String, Integer> entry : linkedHashMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
      }
    }
  

Output:

kiwi: 10
guava: 5
litchi: 8

Conclusion:

`LinkedHashMap` is a useful class in Java when you need to maintain the insertion order of elements in a map. However, it comes with a performance cost compared to `HashMap`. Choose the appropriate map implementation based on the requirements of your application.