Modern software systems often need to perform many tasks at once—such as responding to user input while processing data. Concurrency enables these tasks to make progress independently, improving responsiveness and efficiency.
Rather than completing tasks one after the other, a concurrent system overlaps them, allowing better resource utilization and responsiveness in both single and multi-core environments.
Concurrency in Java refers to the ability of the system to execute multiple tasks simultaneously or in overlapping time periods. Java provides a robust concurrency model using threads, synchronization mechanisms, and high-level concurrent APIs from the java.util.concurrent package.
A clear and simple guide to understanding threads, concurrency, and managing multiple tasks in Java.
class PrintTask implements Runnable {
private String taskName;
public PrintTask(String name) {
this.taskName = name;
}
public void run() {
for (int i = 0; i < 5; i++) {
System.out.println(taskName + " - Count: " + i);
try {
Thread.sleep(500); // Simulate work
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public class ConcurrencyDemo {
public static void main(String[] args) {
Thread t1 = new Thread(new PrintTask("Task 1"));
Thread t2 = new Thread(new PrintTask("Task 2"));
t1.start();
t2.start();
}
}
Manage multiple running processes and handle input/output concurrently.
Allow robots to perform sensing, movement, and communication simultaneously.
Serve multiple clients by spawning a thread for each connection or using thread pools.
Concurrency refers to the ability of a program to perform multiple tasks at the same time by overlapping their execution using multiple threads.
Java supports concurrency through the Thread class, Runnable interface, synchronization mechanisms, and the java.util.concurrent package (Executors, Futures, Locks, etc.).
Concurrency is about dealing with multiple tasks at once (interleaving), while parallelism is about performing multiple tasks at exactly the same time on multiple processors.
Challenges include thread interference, race conditions, deadlocks, and managing thread lifecycle and resource access correctly.