What is the LinkedHashMap.remove(key) method in Java?

A LinkedHashMap is the same as a HashMap, except that a LinkedHashMap maintains the insertion order, whereas a HashMap doesn’t. Internally, the LinkedHashMap uses a doubly-linked list to maintain the insertion order.

The remove method

In LinkedHashMap, we can use the remove method to remove the mapping of the specified key.

Syntax

public V remove(Object key)

Parameters

The key whose mapping is to be removed is passed as an argument.

Return value

  • If there is a mapping present for the specified key, then the mapping is removed and the removed value is returned.

  • If there is no mapping present for the specified key, then null is returned.

Code

The below example shows how to use the remove method.

import java.util.LinkedHashMap;
class RemoveExample {
    public static void main( String args[] ) {
        LinkedHashMap<Integer, String> map = new LinkedHashMap<>();
        map.put(1, "one");
        map.put(2, "two");
        System.out.println("The map is -" + map );
        String returnValue = map.remove(1);
        System.out.println("\nThe return value for remove method is -" + returnValue);
        System.out.println("The map is -" + map );
        
        returnValue = map.remove(3);
        System.out.println("\nThe return value for remove method is -" + returnValue);
        System.out.println("The map is -" + map );
    }
}

Explanation

In the code above:

  • In line 1, we imported the LinkedHashMap class.

  • In line 5, we created a LinkedHashMap object with the name map.

  • In lines 6 and 7, we used the put method to add two mappings ({1=one, 2=two}) to the map object.

  • In line 10, we used the remove method to remove the mapping for the key 1.

  • In line 14, we used the remove method to remove the mapping for the key 3. There is no such entry present, so null will be returned.

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