How to delete all entries in java map.

Remove all entries from java map

Java Map is a data structure that holds key->value pairs. In this article we will see how to delete all entries in the map in java easily and efficetively.

Method clear()

clear() method is method that does not return any thing (void return type) and is part of the Map interface. Each implementation subclasses provides an implementation. clear () methods deleted all entries and turn them map into empty map.
Clear method
static void clearALLItemsInMap() {
		Map<Integer, String> map = new HashMap<Integer, String>();
		map.put(1, "one");
		map.put(2, "two");
		map.put(3, "three");
		map.put(4, "four");
		map.put(5, "five");
		map.put(6, "five");
		newline("Original Map");
		map.forEach( (a,b) -> {
			System.out.println( a + " -> " + b);
                 //clear the map
		newline("After classing clear() Map");
		map.forEach( (a,b) -> {
			System.out.println(a + " -> " + b);
Output of above program.
Original Map
1 -> one
2 -> two
3 -> three
4 -> four
5 -> five
6 -> five

After classing clear() Map


For removing all the entries from java map, clear() method is the best option. Also please note that the clear() method is implemented in each of its implementation classes like, HashMap, TreeMap, LinkedHashMap etc.

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