Java threads are an essential part of the Java programming language. They allow for concurrent execution of multiple tasks within a single program, which can improve the overall performance and responsiveness of the application. However, understanding the lifecycle of a Java thread is crucial to effectively utilizing them in our code. In this blog post, we’ll take a look at the different states a Java thread can be in, and what each state means.
A Java thread can be in one of several states throughout its lifecycle. These states include:
- New: A new thread is in the “new” state when it has been instantiated but has not yet been started yet by calling the
run()method. - Runnable: The thread is in a runnable state after the invocation of
start()method, but the thread scheduler has not selected it to be the running thread. - Running: The thread is in running state if the thread scheduler has selected it and called run() method. (Things to remember here is that we call
start()method notrun()method. The run method calls by the thread scheduler.) - Blocked/Waiting: A thread is in the “blocked” state when it is still alive but is in the waiting state when it is waiting for another thread to perform a specific action.
- Terminated: A thread is in the “terminated” state when it has completed execution by interpreting all the lines inside
run()method or when it has been stopped.
It’s important to note that a thread can transition between these states multiple times throughout its lifecycle. For example, a thread may start in the “new” state, transition to the “runnable” state, then transition to the “blocked” state while waiting for a resource, and finally transition to the “terminated” state once it has completed its task.
In order to effectively use threads in our Java code, it’s important to understand the different states that a thread can be in, and how to properly transition between them. The Thread class, which is part of the Java standard library, provides several methods for controlling the lifecycle of a thread, including start(), sleep(), and join().
In addition, it’s also important to use synchronization and other concurrency constructs to ensure that threads are properly coordinated and that shared resources are accessed in a thread-safe manner.
Conclusion
Understanding the lifecycle of a Java thread is crucial to effectively utilizing them in our code. By understanding the different states a thread can be in, and the methods available for controlling their lifecycle, we can write more efficient and responsive applications. Remember to use synchronization and other concurrency constructs to ensure that threads are properly coordinated and that shared resources are accessed in a thread-safe manner.