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() methodimport 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() methodimport 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.
