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Map clear() method in Java with Example

Last Updated : 31 Dec, 2018

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

Syntax:

void 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.Map.clear() Method:

Program 1:

Mapping String Values to Integer Keys.

Java


 // Java code to illustrate the clear() method
import java.util.*;

public class Map_Demo {
    public static void main(String[] args)
    {
        // Creating an empty Map
        Map<Integer, String> map = new HashMap<Integer, String>();

        // Mapping string values to int keys
        map.put(10, "Geeks");
        map.put(15, "4");
        map.put(20, "Geeks");
        map.put(25, "Welcomes");
        map.put(30, "You");

        // Displaying the Map
        System.out.println("Initial Mappings are: " + map);

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

        // Displaying the final HashMap
        System.out.println("Finally the maps look like this: " + 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


 // Java code to illustrate the clear() method
import java.util.*;

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

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

        // Mapping int values to string keys
        map.put("Geeks", 10);
        map.put("4", 15);
        map.put("Geeks", 20);
        map.put("Welcomes", 25);
        map.put("You", 30);

        // Displaying the Map
        System.out.println("Initial Mappings are: " + map);

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

        // Displaying the final Map
        System.out.println("Finally the maps look like this: " + 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.

Reference

https://docs.oracle.com/javase/7/docs/api/java/util/Map.html#clear()

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