Convert LinkedHashMap to List Java Example

This example shows how to convert LinkedHashMap to a List (ArrayList, LinkedList) in Java. This example also shows how to convert map keys, values, or entries to a List.

How to convert LinkedHashMap to List in Java (ArrayList or LinkedList)?

The LinkedHashMap is an implementation of a Map. The Map and List are two different data structures. The Map stores key-value pairs while the List is an ordered collection of elements.

How to convert all keys of LinkedHashMap to a List?

You can convert all keys of the map object to a List using the keySet method as given below. The keySet method returns a Set view of all keys contained in the map object.

import java.util.ArrayList;

import java.util.LinkedHashMap;

import java.util.List;

public class LinkedHashMapToListExample {

public static void main(String[] args) {

LinkedHashMap<Integer, String> lhmap = new LinkedHashMap<Integer, String>();

lhmap.put(1, "One");

lhmap.put(2, "Two");

lhmap.put(3, "Three");

* To convert LinkedHashMap keys to a List,

* use the keySet method and ArrayList constructor

List<Integer> listKeys = new ArrayList<Integer>( lhmap.keySet() );

System.out.println("List contains:");

for(Integer key : listKeys){

System.out.println(key);

}

Output

List contains:

How to convert all map values to a List?

You can convert all values of the LinkedHashMap to a List using the values method. The values method of the LinkedHashMap class returns a Collection view of all the values contained in the map object. You can then use this collection to convert it to a List object.

LinkedHashMap<Integer, String> lhmap = new LinkedHashMap<Integer, String>();

lhmap.put(1, "One");

lhmap.put(2, "Two");

lhmap.put(3, "Three");

* Get all the values of LinkedHashMap using the

* values method and then add all of them to a List

List<String> listValues = new ArrayList<String>( lhmap.values() );

System.out.println("List contains:");

for(String value : listValues){

System.out.println(value);

}

Output

List contains:

One

Two

Three

How to convert all map entries to a List?

You can also convert all the entries (i.e. key-value pairs or mappings) to a List using the entrySet method. The entrySet method returns a Set view of all the entries contained in the LinkedHashMap object.

LinkedHashMap<Integer, String> lhmap = new LinkedHashMap<Integer, String>();

lhmap.put(1, "One");

lhmap.put(2, "Two");

lhmap.put(3, "Three");

* Get all the entries of LinkedHashMap using the

* entrySet method and then add all of them to a List

List<Map.Entry<Integer, String>> listEntries = new ArrayList<Map.Entry<Integer, String>>( lhmap.entrySet() );

System.out.println("List contains:");

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

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

}

Output

List contains:

1=>One

2=>Two

3=>Three

This example is a part of the LinkedHashMap in Java Tutorial.

Please let me know your views in the comments section below.

References:
Java 8 LinkedHashMap

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Rahim

I have a master's degree in computer science and over 18 years of experience designing and developing Java applications. I have worked with many fortune 500 companies as an eCommerce Architect. Follow me on LinkedIn and Facebook.