What Are Threads?
Explore the fundamentals of Java threads, understanding how they enable multitasking by running multiple execution paths concurrently within a process. Learn about the thread lifecycle, difference between processes and threads, concurrency versus parallelism, and how JVM schedules thread execution to handle complex tasks efficiently.
Up until now, every program we have written has followed a strict, sequential path. We write a line of code, and the computer executes it, then moves to the next. If one line takes five seconds to complete, the entire application halts and waits.
In the real world, however, applications need to do many things at once—a web server handles thousands of requests simultaneously, and a video game renders complex graphics while processing your controller input.
To achieve this in Java, we use threads, independent paths of execution that allow our applications to perform multiple tasks concurrently.
Processes vs. threads
To understand threads, we must first understand the environment they live in: the process.
A process is an instance of a computer program that is being executed. When we start a Java application, the operating system (OS) creates a new process. This process is isolated; it has its own private set of resources and its own allocated memory space that other processes cannot access directly.
A thread (short for “thread of execution”) is a smaller, lightweight unit of execution that lives ...