Structured Concurrency

Structured Concurrency organizes multi-threaded code by treating groups of concurrent tasks running in different threads as a single unit of work, simplifying error handling and cancellation.

Scope Scenarios

Java provides two standard structured concurrency scopes:

• ShutdownOnFailure: Runs tasks in parallel and throws an exception if any task fails. Used for "AND" relations (all results needed).
• ShutdownOnSuccess: Runs tasks in parallel and returns the result of the first successful task, cancelling the rest. Used for "OR" relations (fastest response wins).

Code Walkthrough

This program demonstrates fetching data concurrently using the ShutdownOnFailure scope.

import java.util.concurrent.StructuredTaskScope;
import java.util.function.Supplier;
public class ConcurrencyScopeDemo {
    public static void main(String[] args) throws Exception {
        try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
            // Fork parallel tasks
            Supplier user = scope.fork(() -> "User info");
            Supplier order = scope.fork(() -> "Order details");
scope.join(); // Wait for all forks to complete
            scope.throwIfFailed(); // Propagate errors if any fork failed
System.out.println(user.get() + " & " + order.get());
        }
    }
}

Interview-Relevant Information