How to iterate LinkedHashMap in Java?

LinkedHashMap class extends HashMap and maintains a linked list of the entries in the map, in the order in which they were inserted. This allows insertion-order iteration over the map. That is, when iterating a LinkedHashMap, the elements will be returned in the order in which they were inserted.

There are basically two ways to iterate over LinkedHashMap:

1. Using keySet() and get() Method
2. Using entrySet() and Iterator

Method 1: Iterating LinkedHashMap using keySet() and get() Method

Syntax:

linked_hash_map.keySet()

Parameters: The method does not take any parameter.

Return Value: The method returns a set having the keys of the LinkedHashMap.

• Through keySet() method we will obtain a set having keys of the map.
• And then after running a loop over this set, we can obtain each key and its value using get() method.

Java

// Java Program to iterate through LinkedHashMap using
// keySet() and get() Method

import java.util.LinkedHashMap;
import java.util.Set;

public class GFG {

    public static void main(String a[])
    {
        // making the object of LinkedHashMap
        LinkedHashMap<String, String> linkedHashMap
                 = new LinkedHashMap<String, String>();

        // adding the elements in linkedHashMap
        linkedHashMap.put("One", "First element");
        linkedHashMap.put("Two", "Second element");
        linkedHashMap.put("Three", "Third element");

        Set<String> keys = linkedHashMap.keySet();

        // printing the elements of LinkedHashMap
        for (String key : keys) {
            System.out.println(key + " -- "
                               + linkedHashMap.get(key));
        }

    }
}

Output

One -- First element
Two -- Second element
Three -- Third element

Method 2: Iterating LinkedHashMap using entrySet() and Iterator

Syntax:

Linkedhash_map.entrySet()

Parameters: The method does not take any parameter.

Return Value: The method returns a set having same elements as the LinkedHashMap.

Java

// Java Program to iterate over linkedHashMap using
// entrySet() and iterator

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Set;

public class GFG {

    public static void main(String[] args)
    {

        // Create a LinkedHashMap and populate it with
        // elements
        LinkedHashMap<String, String> linkedHashMap
            = new LinkedHashMap<String, String>();

        // adding the elements to the linkedHashMap
        linkedHashMap.put("One", "First element");
        linkedHashMap.put("Two", "Second element");
        linkedHashMap.put("Three", "Third element");

        // Get a set of all the entries (key - value pairs)
        // contained in the LinkesHashMap
        Set entrySet = linkedHashMap.entrySet();

        // Obtain an Iterator for the entries Set
        Iterator it = entrySet.iterator();

        // Iterate through LinkedHashMap entries
        System.out.println("LinkedHashMap entries : ");

        while (it.hasNext())
            // iterating over each element using it.next()
            // method
            System.out.println(it.next());
    }
}

Output

LinkedHashMap entries : 
One=First element
Two=Second element
Three=Third element