The java.util.HashMap.size() method of HashMap class is used to get the size of the map which refers to the number of the key-value pair or mappings in the Map.
Syntax:
Hash_Map.size()
Parameters: The method does not take any parameters.
Return Value: The method returns the size of the map which also means the number of key-value pairs present in the map.
Below programs illustrates the working of java.util.HashMap.size():
Program 1: Mapping String Values to Integer Keys.
// Java code to illustrate the size() 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); // Displaying the size of the map System.out.println("The size of the map is " + hash_map.size()); }} |
Output:
Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
The size of the map is 5
Program 2: Mapping Integer Values to String Keys.
// Java code to illustrate the size() 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); // Displaying the size of the map System.out.println("The size of the map is " + hash_map.size()); }} |
Output:
Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
The size of the map is 4
Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.
