Java Hashmap remove() Method

June 3, 2023

Methods in Java

A method is a group of code or set of code which is used perform a certain task. We do not need to write code again and again , instead of writing the code we can use these methods. There are two types of methods in java ‘user defined’ and ‘Inbuilt’ methods. The Hashmap class in java also have some inbuilt methods, one of those method is Java Hashmap remove() Method.

To know more about Hashmap remove() Method read the complete article

Java Hashmap remove() Method

The hashmap remove() method is used to remove the specified key and its mapping value from the hashmap. Below in this page you can find it’s syntax, return values, parameters with detailed examples.

Syntax :

hashmap.remove(Object key);

Parameters This method takes one parameter.
Object key : Key whose mapping is to be remove from the hashmap.

Return values :

Value which is mapped to the specified key.
null : If the key is not present in the hashmap.

HashMap putall()

HashMap putifabsent()

HashMap replace()

HashMap size()

HashMap values()

Hashmap remove() Method Examples

Example 1 :

Run

import java.util.*;

public class Main
{
    public static void main (String[]args)
    {

        // Creating an empty HashMap
        HashMap < Integer, String > hash_map_1 =
                new HashMap < Integer, String > ();


        // Mapping string values to int keys in a empty hashmap
        hash_map_1.put (10, "Java");
        hash_map_1.put (20, "Hashmap");
        hash_map_1.put (25, "Remove");
        hash_map_1.put (30, "method");


        //removing the key using remove() method
        String removed=hash_map_1.remove(20);
        
        System.out.println ("Value of removed key is : " + removed);

    }
}

Output :

Value of removed key is : Hashmap

What happened above : In the above example a hashmap is created, initially which is empty and elements are inserted in hash_map_1. hash_map_1.remove(20) is called which gives 'Hashmap' as return value beacause Hashmap is mapped to the key 20.

Example 2 :

Run

import java.util.*;

public class Main
{
    public static void main (String[]args)
    {

        // Creating an empty HashMap
        HashMap < Integer, String > hash_map_1 =
                new HashMap < Integer, String > ();


        // Mapping string values to int keys in a empty hashmap
        hash_map_1.put (10, "Java");
        hash_map_1.put (20, "Hashmap");
        hash_map_1.put (25, "Remove");
        hash_map_1.put (30, "method");


        //removing the key using remove() method
        String removed=hash_map_1.remove(35);
        
        System.out.println ("Value of removed key is : " + removed);

    }
}

Output :

Value of removed key is : null

What happened above : In the above example a hashmap is created and key/values pair are inserted . Then hash_map_1.remove(35) is called which gives null as return value because the key 35 is not mapped to any value in tha hash_map_1.

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Java Hashmap remove() Method

Methods in Java

Java Hashmap remove() Method

Syntax :

Return values :

Hashmap remove() Method Examples

Example 1 :

Output :

Example 2 :

Output :

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