Map remove() Method in Java with Examples

Last Updated : 11 Jul, 2024

The map.remove() method is used to remove the mapping for a key from this map if it is present in the map.

Syntax:

V remove(Object key)

Parameters: This method has the only argument key, whose mapping is to be removed from the map.
Returns: This method returns the value to which this map previously associated the key, or null if the map contained no mapping for the key.
Time Complexity: Average time complexity of O(1) and a worst-case time complexity of O(n).

Map remove() Method in Java

Example 1: The below programs show the implementation of the map.remove() method.

Java

// Java code to show the implementation of // remove method in Map interface import java.util.*; public class GfG {      // Driver code     public static void main(String[] args)     {          // Initializing a Map of type HashMap         Map<Integer, String> map = new HashMap<>();         map.put(1, "One");         map.put(3, "Three");         map.put(5, "Five");         map.put(7, "Seven");         map.put(9, "Nine");         System.out.println(map);          map.remove(3);          System.out.println(map);          // If it doesn't exists, returns         // null and does not affects the map         map.remove(2);          System.out.println(map);     } }

Output

{1=One, 3=Three, 5=Five, 7=Seven, 9=Nine} {1=One, 5=Five, 7=Seven, 9=Nine} {1=One, 5=Five, 7=Seven, 9=Nine}

Explanation of the Program:

This example demonstrates the use of the remove method in the Map interface using a HashMap.
It initializes a HashMap with integer keys and string values, then removes the entry with key 3, and attempts to remove a non-existent key 2.
The output shows the map before and after the removals, illustrating how the remove method works and that attempting to remove a non-existent key has no effect on the map.

Example 2: Below is the code to show implementation of put().

Java

// Java code to show the implementation of // remove method in Map interface import java.util.*; public class GfG {      // Driver code     public static void main(String[] args)     {          // Initializing a Map of type HashMap         Map<String, String> map = new HashMap<>();         map.put("1", "One");         map.put("3", "Three");         map.put("5", "Five");         map.put("7", "Seven");         map.put("9", "Nine");         System.out.println(map);          map.remove("3");          System.out.println(map);     } }

Output

{1=One, 3=Three, 5=Five, 7=Seven, 9=Nine} {1=One, 5=Five, 7=Seven, 9=Nine}

Explanation of the Program:

This program demonstrates the use of the remove method in the Map interface using a HashMap.
It also initializes a HashMap with string keys and values, prints the map, removes the entry with key "3", and then prints the map again to show the result of the removal.
The output illustrates how the remove method affects the map by removing the specified key-value pair.