LinkedHashMap in java

In the previous post, we have seen how to remove elements from HashMap. In this post, we will learn about LinkedHashMap in java.

LinekdHashMap has the following features.

• It implements Map and extends HashMap.
• It differs from HashMap where it maintains a doubly-linked list running through all of its entries.This linked list defines the iteration ordering, which is normally the order in which keys were inserted into the map (insertion-order).
• It maintains the insertion order , where HashMap does not.

Let’s understand LinkedHashMap in java.

Example:

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;

public class HashMapEx {

	public static void  main(String[] args){
		
		LinkedHashMap<Integer,String> hm = new LinkedHashMap<Integer,String>();
		hm.put(15, "Mobile");
		hm.put(6, "TV");
		hm.put(10, "Laptop");
		hm.put(2, "Desktop");
		hm.put(1, "Tablet");
		hm.put(23, "Microphone");
		
		Iterator iter = hm.entrySet().iterator();
		while(iter.hasNext()){
			Map.Entry m = (Entry) iter.next();
			//Maintains insertion order
			System.out.println(m.getKey()+"--"+m.getValue()); 
		}
		
	}
}

Output:

15–Mobile
6–TV
10–Laptop
2–Desktop
1–Tablet
23–Microphone