The HashMap.size()
method in Java is used to return the number of key-value mappings in a HashMap
.
Table of Contents
- Introduction
size
Method Syntax- Examples
- Getting the Size of a HashMap
- Real-World Use Case: Counting Employee Records
- Conclusion
Introduction
The HashMap.size()
method is a member of the HashMap
class in Java. It allows you to determine the number of key-value pairs currently stored in the HashMap
. This can be useful for operations that depend on the size of the map, such as validating data or controlling iterations.
size() Method Syntax
The syntax for the size
method is as follows:
public int size()
- The method does not take any parameters.
- The method returns an
int
value representing the number of key-value mappings in theHashMap
.
Examples
Getting the Size of a HashMap
The size
method can be used to determine the number of entries in a HashMap
.
Example
import java.util.HashMap;
import java.util.Map;
public class SizeExample {
public static void main(String[] args) {
// Creating a Map with String keys and String values
Map<String, String> countries = new HashMap<>();
// Adding entries to the HashMap
countries.put("India", "IN");
countries.put("United States", "US");
countries.put("Canada", "CA");
// Getting the size of the HashMap
int size = countries.size();
// Printing the size of the HashMap
System.out.println("Size of HashMap: " + size);
}
}
Output:
Size of HashMap: 3
Real-World Use Case: Counting Employee Records
In a real-world scenario, you might use the size
method to count the number of employee records in an employee database.
Example
import java.util.HashMap;
import java.util.Map;
public class CountEmployeeRecords {
public static void main(String[] args) {
// Creating a Map with String keys (employee IDs) and String values (employee names)
Map<String, String> employeeDatabase = new HashMap<>();
// Adding entries to the HashMap
employeeDatabase.put("E001", "Ravi Kumar");
employeeDatabase.put("E002", "Priya Sharma");
employeeDatabase.put("E003", "Vijay Singh");
// Getting the size of the employee database
int numberOfEmployees = employeeDatabase.size();
// Printing the number of employee records
System.out.println("Number of Employee Records: " + numberOfEmployees);
}
}
Output:
Number of Employee Records: 3
Conclusion
The HashMap.size()
method in Java provides a way to determine the number of key-value mappings in a HashMap
. By understanding how to use this method, you can efficiently manage and validate the size of your HashMap
in various scenarios. This method is useful for counting entries, validating data size, and controlling iterations based on the number of elements in the map.