Skip to content
Related Articles

Related Articles

Improve Article

HashMap clear() Method in Java

  • Difficulty Level : Medium
  • Last Updated : 26 Nov, 2018
Geek Week

The java.util.HashMap.clear() method in Java is used to clear and remove all of the elements or mappings from a specified HashMap.

Syntax:

Hash_Map.clear()

Parameters: The method does not accept any parameters.

Return Value: The method does not return any value.

Below programs are used to illustrate the working of java.util.HashMap.clear() Method:
Program 1: Mapping String Values to Integer Keys.






// Java code to illustrate the clear() method
import java.util.*;
  
public class Hash_Map_Demo {
    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, "Geeks");
        hash_map.put(15, "4");
        hash_map.put(20, "Geeks");
        hash_map.put(25, "Welcomes");
        hash_map.put(30, "You");
  
        // Displaying the HashMap
        System.out.println("Initial Mappings are: " + hash_map);
  
        // Clearing the hash map using clear()
        hash_map.clear();
  
        // Displaying the final HashMap
        System.out.println("Finally the maps look like this: " + hash_map);
    }
}
Output:
Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
Finally the maps look like this: {}

Program 2: Mapping Integer Values to String Keys.




// Java code to illustrate the clear() method
import java.util.*;
  
public class Hash_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty HashMap
        HashMap<String, Integer> hash_map = new HashMap<String, Integer>();
  
        // Mapping int values to string keys
        hash_map.put("Geeks", 10);
        hash_map.put("4", 15);
        hash_map.put("Geeks", 20);
        hash_map.put("Welcomes", 25);
        hash_map.put("You", 30);
  
        // Displaying the HashMap
        System.out.println("Initial Mappings are: " + hash_map);
  
        // Clearing the hash map using clear()
        hash_map.clear();
  
        // Displaying the final HashMap
        System.out.println("Finally the maps look like this: " + hash_map);
    }
}
Output:
Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
Finally the maps look like this: {}

Note: The same operation can be performed with any type of Mapping with variation and combination of different data types.

Attention reader! Don’t stop learning now. Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.




My Personal Notes arrow_drop_up
Recommended Articles
Page :