When it comes to concurrent programming in Java, understanding thread priority is essential. Threads are lightweight processes that run concurrently within an application, and managing their execution order and behavior can greatly impact the performance and responsiveness of your program.
In this blog, we’ll go through what is thread priority in Java, how it works, and how you can use it effectively with examples.
So, before understanding what thread priority is in Java, let’s first understand what is thread in Java?
Also Read: What Is Java Programming Language
What Is Thread In Java ?
In Java, a thread is a separate path of execution within a program. It is mainly used for multitasking, allowing multiple tasks to be performed simultaneously . Each thread represents an independent flow of control, with its own stack and program counter.
What is Thread Priority?
levels of importance. Each thread is given a priority number from 1 to 10 (from lowest to Highest). All threads have a rating of 5 by default, which means they are all the same. The JVM scheduler uses these priorities to decide which threads to run and in what order.
Note: Thread priority does not guarantee the order of execution, as it relies on factors like the operating system and the JVM implementation.
Setting Thread Priority
To set the priority of a thread in Java, you can use the “setPriority()” method provided by the “Thread class”.
It’s worth mentioning that thread priority is an integer value, so you can also use the constants defined in the “Thread class”, such as –
Thread Priority Levels:
Now, let’s examine the three pre-defined levels of thread priority in more detail
- MIN_PRIORITY (1)
- NORM_PRIORITY (5)
- MAX_PRIORITY (10)
1. MIN_PRIORITY (1)
This represents the lowest priority level. Threads with this priority are considered the least important and are typically scheduled last by the JVM. These threads are assigned CPU time only when no higher priority threads are waiting to run.
2. NORM_PRIORITY (5)
This is the default priority level assigned to all threads. Threads with this priority are given fair access to CPU time and share it equally with other threads of the same priority.
3. MAX_PRIORITY (10)
This is the highest priority level. Threads with this priority are considered the most important and are scheduled first by the JVM.
Note: Assigning a thread the maximum priority does not guarantee it will always execute before other threads.
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Example Of Thread Priority In Java
Let’s consider an example scenario where thread priority can be beneficial. Suppose you have an application that involves real-time audio processing and user interface rendering. In this case, you can assign a higher priority to the audio processing thread to ensure smooth and uninterrupted playback.
In this code, we have two threads: “audioThread” and “uiThread”. The audioThread is responsible for real-time audio processing, and the uiThread handles user interface rendering.
We set the priority of the “audioThread” to “Thread.MAX_PRIORITY” to prioritize its execution over the “uiThread”, which has a priority of “Thread.NORM_PRIORITY” (default priority level).
Both threads are started using the “start()” method, which initiates their execution concurrently.
The logic inside each thread’s “run()” method simulates their respective tasks by printing numbers from 1 to 10 with a delay to simulate processing time.
When you run this code, you will notice that the “audioThread” executes more frequently compared to the “uiThread”, thanks to its higher priority.
Also Read: Java Interview Questions
Thread Scheduling In Java
Now let’s see how threads are scheduled in Java. The JVM’s scheduler uses an algorithm for scheduling based on prioritization and interruption.
Therefore, higher priority threads are more likely to be performed first.
But the exact way thread scheduling works relies on the operating system & how the JVM is implemented.
Different operating systems may have different thread schedulers, which can impact the effectiveness of thread priorities.
Therefore, it’s very important to consider thread priority as a hint rather than a strict directive.
Best Practices for Using Thread Priority
While thread priority can be helpful in specific situations, it is essential to use it wisely.
Here are some best practices to keep in mind:
1. Avoid relying solely on thread priority
Instead of relying only on thread priority, make your program thread-safe and use locks and semaphores to keep threads from interfering with each other.
2. Avoid excessive use of thread priority
Assigning extreme priorities to threads can lead to unpredictable behavior and make your application harder to reason about. Use thread priority as a last resort when other synchronization mechanisms are insufficient.
3. Test on multiple platforms
Because the way threads are scheduled can be different on different platforms, it is important to test your app on multiple systems to make sure it works the same way everywhere.
Thread priority in Java provides a mechanism to assign relative importance to different threads within your application. Understanding thread priority and its limitations will help you design better concurrent applications. By combining thread priority with synchronization mechanisms, you can create more robust and responsive programs.
Keep exploring and experimenting with Java threads, and don’t forget to think about thread safety and synchronization when making apps that run at the same time. Good luck coding!
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