ArrayBlockingQueue

ArrayBlockingQueue is a bounded blocking queue backed by an array. It is a thread-safe implementation of the Queue interface from the Java Collections Framework. The capacity of the queue is fixed at construction time and cannot be changed afterwards. When the queue is full, attempting to add elements will result in blocking until space becomes available. Similarly, attempting to remove elements from an empty queue will block until an element is added.

Key characteristics of ArrayBlockingQueue include its fixed size, ensuring that it will never grow beyond its initial capacity. This boundedness can be useful for resource management, preventing unbounded memory consumption. Operations like adding (offer, put) and removing (poll, take) elements are atomic, meaning they are executed as a single, indivisible unit, ensuring thread safety.

ArrayBlockingQueue offers two main modes for insertion: a fair mode and an unfair mode. In fair mode, threads waiting to add or remove elements are granted access to the queue in the order they arrived. In unfair mode, which is the default, there is no guarantee of ordering, potentially allowing newly arriving threads to access the queue before those that have been waiting longer. The choice between fair and unfair modes can impact performance.

Common use cases for ArrayBlockingQueue include producer-consumer scenarios where one or more threads produce data and one or more threads consume it. Its blocking nature simplifies the synchronization logic required for such patterns, as producers wait when the queue is full and consumers wait when it is empty, thus coordinating their activities without explicit locks in many cases.