What is concurrency in Java?

Concurrency refers to the ability of a program to perform multiple tasks simultaneously or in parallel, with the aim of improving performance and responsiveness. Concurrency allows multiple threads, processes or tasks to execute concurrently and share the same resources, such as CPU, memory, and input/output devices, while maintaining data consistency and correctness.

Concurrency is a fundamental concept in modern software development, as it allows programs to take full advantage of the multiple processors, cores and other hardware resources available in modern computing systems. It is used in a wide range of applications, from web servers handling multiple requests simultaneously to desktop applications that can perform background tasks while the user interacts with the program.

However, concurrency also introduces new challenges and complexities, such as race conditions, deadlocks, and synchronization issues. These issues arise when multiple threads or processes try to access the same resource simultaneously, leading to unpredictable and undesirable behavior.

To address these challenges, developers use various techniques and tools, such as locks, semaphores, and atomic operations, to synchronize access to shared resources and ensure data consistency and correctness. Additionally, modern programming languages and frameworks often provide higher-level abstractions and libraries to help developers write concurrent code more easily and efficiently.