The CopyOnWriteArrayList.size()
method in Java is used to get the number of elements in a CopyOnWriteArrayList
.
Table of Contents
- Introduction
size
Method Syntax- Examples
- Getting the Size of a CopyOnWriteArrayList
- Size After Adding and Removing Elements
- Real-World Use Case
- Example: Monitoring the Size of a Thread-Safe User List
- Conclusion
Introduction
The CopyOnWriteArrayList
is a thread-safe variant of ArrayList
in Java. It is part of the java.util.concurrent
package and is designed for scenarios where read operations are more frequent than write operations. The size
method allows you to determine the number of elements currently stored in the list. The CopyOnWriteArrayList
achieves thread safety by creating a new copy of the array whenever it is modified.
size() Method Syntax
The syntax for the size
method is as follows:
public int size()
- The method takes no parameters.
- The method returns an integer representing the number of elements in the list.
Examples
Getting the Size of a CopyOnWriteArrayList
The size
method can be used to get the number of elements in a CopyOnWriteArrayList
.
Example
import java.util.concurrent.CopyOnWriteArrayList;
public class SizeExample {
public static void main(String[] args) {
// Creating a CopyOnWriteArrayList with String elements
CopyOnWriteArrayList<String> names = new CopyOnWriteArrayList<>();
// Adding elements to the CopyOnWriteArrayList
names.add("Ravi");
names.add("Priya");
names.add("Vijay");
// Getting the size of the CopyOnWriteArrayList
int size = names.size();
// Printing the size
System.out.println("Size of CopyOnWriteArrayList: " + size);
}
}
Output:
Size of CopyOnWriteArrayList: 3
Size After Adding and Removing Elements
The size
method reflects changes in the list after adding or removing elements.
Example
import java.util.concurrent.CopyOnWriteArrayList;
public class AddRemoveSizeExample {
public static void main(String[] args) {
// Creating a CopyOnWriteArrayList with String elements
CopyOnWriteArrayList<String> names = new CopyOnWriteArrayList<>();
// Adding elements to the CopyOnWriteArrayList
names.add("Ravi");
names.add("Priya");
names.add("Vijay");
// Printing the initial size
System.out.println("Initial size: " + names.size());
// Removing an element
names.remove("Priya");
// Printing the size after removal
System.out.println("Size after removal: " + names.size());
// Adding a new element
names.add("Anita");
// Printing the final size
System.out.println("Final size: " + names.size());
}
}
Output:
Initial size: 3
Size after removal: 2
Final size: 3
Real-World Use Case
Example: Monitoring the Size of a Thread-Safe User List
A common real-world use case for CopyOnWriteArrayList
is managing a thread-safe list of users and monitoring the number of users.
Example
import java.util.concurrent.CopyOnWriteArrayList;
public class UserListManager {
public static void main(String[] args) {
// Creating a CopyOnWriteArrayList to manage user names
CopyOnWriteArrayList<String> userList = new CopyOnWriteArrayList<>();
// Adding user names to the CopyOnWriteArrayList
userList.add("Ravi");
userList.add("Priya");
userList.add("Vijay");
// Simulating concurrent read and write operations
Thread readerThread = new Thread(() -> {
int size = userList.size();
System.out.println("Number of users: " + size);
});
Thread writerThread = new Thread(() -> {
userList.add("Anita");
System.out.println("Added user: Anita");
});
// Starting the threads
readerThread.start();
writerThread.start();
// Waiting for the threads to finish
try {
readerThread.join();
writerThread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
// Printing the final user list size
System.out.println("Final number of users: " + userList.size());
}
}
Output:
Number of users: 3
Added user: Anita
Final number of users: 4
In this example, CopyOnWriteArrayList
is used to manage a thread-safe list of user names, allowing concurrent read and write operations while monitoring the number of users.
Conclusion
The CopyOnWriteArrayList.size()
method in Java provides a way to get the number of elements in a CopyOnWriteArrayList
in a thread-safe manner. By understanding how to use this method, you can efficiently manage collections of elements in your Java applications, especially in concurrent environments. The method allows you to monitor the size of the list, making it a versatile tool for data management in multi-threaded scenarios.