What is the LinkedHashMap.entrySet method in Java?

A LinkedHashMap is the same as a regular HashMap, except that a LinkedHashMap maintains the insertion order, whereas a HashMap does not.

Internally, the LinkedHashMap uses a doubly-linked list to maintain the insertion order.

The `entrySet` method

In a LinkedHashMap, we can use the entrySet method to get all the entrieskey-value mappings of the LinkedHashMap object as a set view.

Syntax

public Set<Map.Entry<K,V>> entrySet()

Parameters

This method doesn’t take any parameters.

Return value

The entrySet method returns a set view of all of the entries in the map.

Code

The example below shows how to use the entrySet method.

import java.util.LinkedHashMap;
import java.util.Set;
import java.util.Map;
class EntrySetExample {
    public static void main( String args[] ) {
        LinkedHashMap<Integer, String> map = new LinkedHashMap<>();
        map.put(1, "one");
        map.put(2, "two");
        
        System.out.println("The map is -" + map );
        Set<Map.Entry<Integer, String>> entries = map.entrySet();
        System.out.println("The entries are -" +   entries);
        System.out.println("\nAdding a new entry 4 - four to the map" );
        map.put(4, "four");
        System.out.println("After adding the entries are -" + entries);
    }
}

Explanation

In the code above:

In line 1, we import the LinkedHashMap class.
In line 7, we create a LinkedHashMap object with the name map.
In lines 8 and 9, we use the put method to add two mappings ({1=one, 2=two}) to the map object.
In line 13, we get the entries of the LinkedHashMap with the entrySet method and store them in the entries variable.
In line 17, we add a new entry 4 - "four" to the map.
In line 19, we print entries. The newly added entry, 4 - "four", will automatically be available in the entries variable without the need to call the entrySet method because the entrySet method returns the set view.

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