How to Convert a Map to a List in Java?

Dec 31, 2019

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A Map maps keys to values. Map provides following two methods to return keys and values of a map:

public Collection<V> values()	This method returns a Collection view of the values contained in this map.
public Set keySet()	This method returns a Set view of the keys contained in this map

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Set;

public class MapToListExample {
	public static void main(String[] args) {
		HashMap map = new HashMap();
		map.put("key1", "value1");
		map.put("key2", "value2");
		map.put("key3", "value3");
		map.put("key4", "value4");
		map.put("key5", "value5");
		
		//values method returns a collection of values
		List<String> values = new ArrayList(map.values());

		System.out.println("Values: " + values);
		
		//keySet() method returns a set of keys
		Set keys = map.keySet();

		System.out.println("keys: " + keys);
	}
}

Output

Values: [value1, value2, value5, value3, value4]
keys: [key1, key2, key5, key3, key4]