The LinkedHashMap.size()
method in Java is used to determine the number of key-value mappings in a LinkedHashMap
.
Table of Contents
- Introduction
size
Method Syntax- Examples
- Determining the Size of a LinkedHashMap
- After Adding and Removing Entries
- Real-World Use Case
- Example: Tracking the Number of Active Users
- Conclusion
Introduction
The LinkedHashMap.size()
method is a member of the LinkedHashMap
class in Java. It allows you to determine the number of key-value pairs currently stored in the map. This can be useful in scenarios where you need to know the size of the map, such as for validating the map’s state or for iteration purposes.
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 the number of key-value pairs in the map as an
int
.
Examples
Determining the Size of a LinkedHashMap
The size
method can be used to get the number of key-value pairs in a LinkedHashMap
.
Example
import java.util.LinkedHashMap;
public class SizeExample {
public static void main(String[] args) {
// Creating a LinkedHashMap with String keys and Integer values
LinkedHashMap<String, Integer> people = new LinkedHashMap<>();
// Adding entries to the LinkedHashMap
people.put("Ravi", 25);
people.put("Priya", 30);
people.put("Vijay", 35);
// Getting the size of the LinkedHashMap
int size = people.size();
// Printing the size of the LinkedHashMap
System.out.println("Size of LinkedHashMap: " + size);
}
}
Output:
Size of LinkedHashMap: 3
After Adding and Removing Entries
The size
method reflects the current number of key-value pairs in the map, which can change after adding or removing entries.
Example
import java.util.LinkedHashMap;
public class ModifySizeExample {
public static void main(String[] args) {
// Creating a LinkedHashMap with String keys and Integer values
LinkedHashMap<String, Integer> people = new LinkedHashMap<>();
// Adding entries to the LinkedHashMap
people.put("Ravi", 25);
people.put("Priya", 30);
people.put("Vijay", 35);
// Printing the initial size of the LinkedHashMap
System.out.println("Initial size of LinkedHashMap: " + people.size());
// Removing an entry from the LinkedHashMap
people.remove("Priya");
// Printing the size of the LinkedHashMap after removal
System.out.println("Size of LinkedHashMap after removal: " + people.size());
}
}
Output:
Initial size of LinkedHashMap: 3
Size of LinkedHashMap after removal: 2
Real-World Use Case
Example: Tracking the Number of Active Users
A common real-world use case for LinkedHashMap.size()
is tracking the number of active users in an application. For example, let’s consider a scenario where user sessions are stored in a LinkedHashMap
, and we need to determine the number of active user sessions.
Example
import java.util.LinkedHashMap;
public class ActiveUserTracker {
public static void main(String[] args) {
// Creating a LinkedHashMap to store user sessions
LinkedHashMap<String, String> userSessions = new LinkedHashMap<>();
// Adding some user sessions
userSessions.put("Ravi", "Active");
userSessions.put("Priya", "Active");
userSessions.put("Vijay", "Inactive");
// Getting the number of active user sessions
int activeUserCount = 0;
for (String status : userSessions.values()) {
if (status.equals("Active")) {
activeUserCount++;
}
}
// Printing the number of active user sessions
System.out.println("Number of active user sessions: " + activeUserCount);
}
}
Output:
Number of active user sessions: 2
In this example, LinkedHashMap.size()
is used to determine the number of key-value pairs, and additional logic is applied to count only the active sessions, demonstrating how to use the method in conjunction with other operations.
Conclusion
The LinkedHashMap.size()
method in Java provides a way to determine the number of key-value pairs in a LinkedHashMap
. By understanding how to use this method, you can efficiently manage collections of key-value pairs in your Java applications. The method allows you to verify the map’s state, making it a versatile tool for data management and validation.