Multithreading is the ability of an operating system to have numerous threads in memory at the same point in time with the illusion that all these threads are executing concurrently. While multithreading provides several benefits, you must be aware of the best practices to avoid any issues related to thread synchronization, starvation, concurrency, and so forth.
In this programming tutorial, we will examine the best practices for multithreading in Java.
Before getting started, you may want to read our tutorial: Introduction to Multithreading in Java.
Multithreading Best Practices in Java Software Development
Below are some of the best practices developers should use when working with multiple threads in Java applications.
Avoid Race Conditions and Deadlocks
The most pertinent thing to remember when working with Java threads is to avoid race conditions and deadlocks. A race condition can occur when multiple threads attempt to access the same piece of data at the same point of time.
Programmers may experience unexpected results as a result of this, and it may cause you to encounter problems with your program. Deadlocks happen when threads wait for each other to finish before continuing. It may be challenging to debug and solve this problem because it can cause the program to freeze up.
Use Synchronization When Accessing Shared Resources
Proper usage of thread synchronization prevents race conditions and is the best practice when working with multiple threads that might access shared resources. When accessing shared resources from multiple threads, use thread-safe methods or synchronized blocks for mutable objects. Do not access shared resources without first obtaining a lock on them.
Avoid using wait() and notify()
While the wait() and notify() methods may seem like an efficient way to manage threads, they can lead to deadlock situations if not used correctly. It is usually better to use the other synchronization techniques instead.
Use Thread Pools
Developers can leverage thread pools in Java to limit the number of active threads in a program. This reduces the overhead associated with creating and managing threads. Thread pools can help to reduce the overhead of creating, managing, and destroying threads.
Thread pools allow programmers to create a set number of threads that can be reused for tasks, eliminating the need for creating new threads every time you need to execute something.
When using thread pools, it is necessary to consider the pool size carefully. It would help if you sized the pool appropriately to handle peak loads while avoiding unnecessary thread creation.
You can learn more about thread pools in our tutorial: Introduction to Thread Pools in Java.
Prioritize Lock Ordering
When working with synchronized blocks or methods, it is important to order the locks in such a way that two threads do not try to acquire the same locks at the same time, leading to deadlocks. The lock order should always be based on which objects are most likely to be accessed first by other threads, in order to reduce chances of deadlock occurring.
Use Volatile Fields
Volatile fields are a good idea when using threads in Java. Volatile fields can be changed by multiple threads and written and read by multiple threads. By using volatile fields, you make sure all threads see the most recent value. This is important for ensuring data consistency across threads.
In Java, volatile fields are declared using the volatile keyword. When developers are writing to a volatile field, all writes are instantly visible to the other threads. As a result, other threads will always see the latest value. Similarly, when reading from a volatile field, all reads are guaranteed to return the most recent write by any thread.
Because of this guarantee, volatile fields are often used as a simple form of synchronization between threads. For example, a thread might use a volatile field as a flag to indicate that some operation has been completed.
Another thread can check this flag to know when it is safe to proceed. Volatile fields do not guarantee proper ordering, though. In other words, if one thread writes to a volatile field and another reads from it, the order in which the reads and writes take place is not guaranteed. There is only one guarantee: it will return the most recent write.
Avoid Using Thread-local Variables
Thread-local variables should be used sparingly, because they can quickly become difficult to manage and maintain in complex applications involving many threads and objects. In general, it is better to avoid using thread-local variables unless absolutely necessary.
Keep Synchronization Blocks Fast
Synchronization blocks should be kept as small as possible for maximum performance and scalability. Avoid calling expensive operations inside synchronization blocks or making any calls that can block (such as I/O calls) whenever possible.
Use Lock-free Data Structures
Lock-free data structures are designed to reduce contention and increase scalability. Consider using them when you need to access shared resources from multiple threads in an efficient manner.
Creating new threads and running them in a multithreaded environment incurs costs, mainly due to context switching. You can take advantage of the Java Executor Framework, a part of the Java concurrency package introduced in Java 1.5. It is a wrapper on the main Java runtime threading infrastructure.
Executors are a Java utility class that makes it easier to manage and execute tasks in a thread-pool. Consider using an executor to manage your application’s threads instead of managing them manually.
You can learn more about this technique in our tutorial: Using the Executor Framework to Deal with Java Threads.
Use Thread-safe Logging
Logging is one of the most important cross-cutting concerns in any application. That said, it can be extremely challenging to implement it in a multi-threaded environment. Make sure to use thread-safe logging libraries or frameworks to ensure that logs are properly written in a thread-safe and consistent manner.
Monitor and Log Performance
Monitor the performance of threads in your application and make sure to log any problems that arise and identify potential bottlenecks or issues in your application before they become major problems.
Utilize Thread-safe Libraries
There are many third-party libraries and frameworks that provide thread-safe implementations of common operations. Consider using these whenever possible to reduce the amount of manual thread management you have to do.
Use Read/Write Locks When Multithreading in Java
In Java, Read/Write locks allow multiple threads to have simultaneous read-only access to a resource, but only one thread can have write access at a time. This ensures that no two threads are writing to the resource at the same time, which can cause data corruption.
There are a few things to keep in mind when using Read/Write locks in Java:
- Make sure that all write operations are performed within a lock block. This will ensure that only one thread will be able to write to the resource at a particular point of time.
- When possible, use tryLock() instead of lock() to acquire a lock. The tryLock() method will return false if the lock is already held by another thread, which can save your thread from blocking unnecessarily.
- Be sure to release the lock as soon as possible after finishing with the resource. Holding a lock for too long can prevent other threads from accessing the resource they need.
Use the Correct Concurrent Collection
Concurrent collections are designed to handle multiple threads accessing the same data structure in a safe and efficient manner. For example, if you need to store large amounts of data that is frequently accessed or modified, consider using a ConcurrentHashMap instead of a Vector.
You can learn more about this method in our tutorial: Introduction to ConcurrentHashMap in Java.
Use Atomic Objects
When working with threads in Java, it is important to use atomic objects to ensure that data is manipulated correctly. Atomic objects provide a simple way to ensure that data is accessed and updated in a thread-safe manner. Some of the atomic classes in Java include AtomicInteger,AtomicLong, AtomicBoolean, and AtomicReference.
Final Thoughts on Java Multithreading Best Practices
Following the best practices for Java multithreading in this programming tutorial, developers can reduce their risk of encountering threading issues and create robust code that takes advantage of multithreading without introducing unnecessary complications.
Always use thread-safe classes, methods, and variables for better efficiency and scalability. With good design choices, developers can implement efficient multithreaded Java applications that increase performance while maintaining efficiency.