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 code to illustrate the clear() methodimport 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 code to illustrate the clear() methodimport 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()
