Java Hashmap clear() Method

July 20, 2023

What is a Hashmap?

Hashmap was first introduced in Java 1.2.The Hashmap class is included in the java.util package.The data in a hashmap is stored in two parts: the key and the value, which can be accessed using an index of another type.A hashmap have unique keys , inserting a duplicate key will replace the data of the key.

Hashmap class have many inbuilt method, one of those method is hashmap clear(). To know more about Java Hashmap clear() method read the complete article

Java Hashmap clear() Method

The hashmap clear() method clears the data of a hashmap , the keys and the values. this method does not take any parameters. Below in this page you can find it’s syntax, return values, parameters with detailed examples.

Syntax :

hashmap.clear();

Parameters :

This method does not take any parameters

Return values :

This method does not return any values

Classes in Java

Access modifiers in Java

Abstract classes in Java

Constructor in Java

Hashmap clear() Method Examples

Example :

Run

import java.util.*;

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

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

    // Mapping string values to int keys
    hash_map.put (10, "Java");
    hash_map.put (20, "Hashmap");
    hash_map.put (25, "clear");
    hash_map.put (30, "method");

    // Displaying the HashMap
    System.out.println ("Initial :" + hash_map);

    // Clearing the hash map using clear()
    hash_map.clear ();

    // Displaying the final HashMap
    System.out.println ("Finally the hashmap is empty: " + hash_map);
  }
}

Output :

Initial :{20=Hashmap, 25=clear, 10=Java, 30=method}
Finally the hashmap is empty: {}

What happened above: In the above example a hashmap is created and elements are inserted in the hashmap. When the clear() method caleed it removes the key and the value corresponding to that key.

Note In Java the functionality of clear() method can be achieved by reinitializing the hashmap.

Example :

Run

import java.util.*;

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

        // Creating an empty HashMap
        HashMap hash_map = new HashMap();

        // Mapping string values to int keys
        hash_map.put(10, "Java");
        hash_map.put(20, "Hashmap");
        hash_map.put(25, "clear");
        hash_map.put(30, "method");

        // Displaying the HashMap
        System.out.println("Initial :" + hash_map);

        // reaimnitializing the hashmap
        hash_map=new HashMap<>();

        // Displaying the final HashMap
        System.out.println("Final : " + hash_map);
      
    }
}

Output :

Initial :{20=Hashmap, 25=clear, 10=Java, 30=method}
Final : {}

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Java Hashmap clear() Method

What is a Hashmap?

Java Hashmap clear() Method

Syntax :

Parameters :

Return values :

Hashmap clear() Method Examples

Example :

Output :

Example :

Output :

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