How to convert a Map to List in Java?

List<Value> list = new ArrayList<Value>(map.values());

assuming:

Map<Key,Value> map;

The issue here is that Map has two values (a key and value), while a List only has one value (an element).

Therefore, the best that can be done is to either get a List of the keys or the values. (Unless we make a wrapper to hold on to the key/value pair).

Say we have a Map:

Map<String, String> m = new HashMap<String, String>();
m.put("Hello", "World");
m.put("Apple", "3.14");
m.put("Another", "Element");

The keys as a List can be obtained by creating a new ArrayList from a Set returned by the Map.keySet method:

List<String> list = new ArrayList<String>(m.keySet());

While the values as a List can be obtained creating a new ArrayList from a Collection returned by the Map.values method:

List<String> list = new ArrayList<String>(m.values());

The result of getting the List of keys:

Apple
Another
Hello

The result of getting the List of values:

3.14
Element
World

Using the Java 8 Streams API.

List<Value> values = map.values().stream().collect(Collectors.toList());