Understanding the Executor Framework in Java With Interview question

Overview

The ExecutorService interface is part of the java.util.concurrent package and represents an asynchronous task execution service. It extends the Executor interface, which defines a single method execute(Runnable command) for executing tasks.

Understanding the Executor Framework in Java With Interview question

Executors

The Executors class in Java is a utility class that provides factory methods for creating and managing different types of ExecutorService instances. It simplifies the process of instantiating thread pools and allows developers to easily create and manage executor instances with various configurations.

Types of Executor Services

The Executors class provides several static factory methods for creating different types of executor services:

1. FixedThreadPool

Creates an ExecutorService with a fixed number of threads. Tasks submitted to this executor are executed concurrently by the specified number of threads. If a thread is idle and no tasks are available, it remains alive but dormant until needed.

ExecutorService executor = Executors.newFixedThreadPool(5);

2. CachedThreadPool

Creates an ExecutorService with an unbounded thread pool that automatically adjusts its size based on the workload. Threads are created as needed and reused for subsequent tasks. If a thread remains idle for a certain period, it may be terminated to reduce resource consumption.

In a cached thread pool, submitted tasks are not queued but immediately handed off to a thread for execution. If no threads are available, a new one is created. If a server is heavily loaded and all CPUs are fully utilized, more threads will be created, which can worsen the situation. The default idle time for threads is 60 seconds; after that, if they don’t have any tasks, the thread will be terminated.

Therefore, in a heavily loaded production server, it’s better to use Executors.newFixedThreadPool, which provides a fixed number of threads, or use the ThreadPoolExecutor class directly for maximum control.

ExecutorService executor =…