How to Convert HashMap to List

author-imageBy Dhiraj, 19 October,2016   1K

HashMap is a class in Java that implements Map interface.It is an unsorted and unordered map whereas ArrayList implements List interface and maintains insertion order.Here we will try to convert a HashMap into an ArrayList.

Let us define a HashMap first.

Map<String, String> map = new HashMap<String, String>();

At first,let us see how to get list of keys from a HashMap.There is an implicit method defined in java library to get the list of keys of a HashMap.And after getting the list of keys, construct an ArrayList with it.

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

//list of all the keys defined in Hashmap
ArrayList<String> listOfKeys = new ArrayList<String>(keys);

Similarly, extract the values of a HashMap and construct an ArrayList out of it as below:

Collection<String> values = map.values();

//list of all the values defined in Hashmap
ArrayList<String< listOfValues = new ArrayList<String>(values);

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Now let us constuct a single ArrayList having both the keys and values of a HashMap in a single shot.

Set<Entry<String, String>> entrySet = map.entrySet();
ArrayList<Entry<String, String>> listOfEntries = new ArrayList<Entry<String, String>>(entrySet);

for (Entry<String, String> entry : listOfEntries) {
	System.out.println(entry.getKey() + " : " + entry.getValue());


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Further Reading on Core Java

1. Sorting Hashmap By Key And Value

2. Why Wait Notify Notifyall Defined In Object Class

3. Comparable And Comparator In Java With Example

4. Random Password Generator Java

5. Serialization And Deserialization Java Example

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