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); } } |
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); } } |
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.
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