LinkedHashMap implementation in java

               It is a type of map which extends ‘Map’ from java collections Framework. Here, a doubly linked list is used. This uses either insertion-order or access order to iterate the linked list.

Features:

• ·       The iteration follows either insertion order or access order.
• ·       The performance is balanced among the prediction of iterations and operations.
• ·       It allows one null key and multiple null values.

Implementation of LinkedHashMap in java:

              This program creates some data structures with number of elements for mapping.

Steps:

• ·       First, import the built in packages java.util.LinkedHashMap and java.util.Map.
• ·       Create a public class with main() function.
• ·       An object instance is created for LinkedHashMap.
• ·       Using the object, the key,value pair is added to the linkedHashMap.
• ·       Function get() is used to retrieve and display the key,value pair.
• ·       ContainsKey() member function finds a key,value pair is available in the map.
• ·       getKey(),getValue() retrive the key,value from the map.
• ·       To delete a key,value pair, remove() function is used.
• ·       Clear() function clears the entire elements.
• ·       isEmpty() returns true when the map is empty.

Program:

import java.util.LinkedHashMap;

import java.util.Map;

public class LinkedHashMapEg {

    public static void main(String[] args) {

        // Create an object for LinkedHashMap

        Map<String, Integer> linkedHashMap1 = new LinkedHashMap<>();

        // insert the key-value pairs to the linkedHashMap

        linkedHashMap1.put("LinkedList", 50);

        linkedHashMap1.put("Stack", 20);

        linkedHashMap1.put("Queue", 30);

        linkedHashMap1.put("Tree", 40);

        linkedHashMap1.put("Binary Tree",45);

        // Extract a data

        System.out.println("Number of elements in Queue: " + linkedHashMap1.get("Queue"));

        // Check a key's availability

        if (linkedHashMap1.containsKey("Tree")) {

            System.out.println("Tree is available.");

        }

        // Create a loop to display the key,value in LinkedHashMap

        for (Map.Entry<String, Integer> entry : linkedHashMap1.entrySet()) {

            System.out.println(entry.getKey() + ": " + entry.getValue());

        }

         // Delete a key-value pair

        linkedHashMap1.remove("Binary Tree");

        // Print the size of the LinkedHashMap

        System.out.println("Size of the LinkedHashMap: " + linkedHashMap1.size());

        // Clear all the key,value pair in the LinkedHashMap

        linkedHashMap1.clear();

        // Check the linkedHashMap is empty or not

        if(linkedHashMap1.isEmpty())

        System.out.println("LinkedHashMap is empty");

    }

}

Output:

C:\raji\blog>javac LinkedHashMapEg.java

C:\raji\blog>java LinkedHashMapEg

Number of elements in Queue: 30

Tree is available.

LinkedList: 50

Stack: 20

Queue: 30

Tree: 40

Binary Tree: 45

Size of the LinkedHashMap: 4

LinkedHashMap is empty

This is the simple way of implementing LinkedHashMap program in java. Hope, this post will be useful for you. Keep coding!!!